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ANACARDIACEAE(Cashew family)
The 60 genera comprising some 600 species of trees and shrubs are distributed throughout he tropics, and are also found in warm temperate regions of Europe, eastern Asia, and the Americas. Many species have been widely cultivated beyond their limited areas of origin because of their economic importance as sources of timber, lacquer, oil, wax, dye, and for their often edible fruit or nuts. The most important fruit is the mango from Mangifera indica L., whilst the most important nut is the cashew from Anacardium occidentale L. Dyes may be obtained from the leaves of Rhus copallina L. (syn. Schmalzia copallina Small), the wood of Rhus cotinoides Nutt. (syn. Cotinus americanus Nutt.), the roots of Rhus glabra L., the galls of Rhus chinensis Mill., etc. Because of the tannin content of the leaves or bark, several species including Rhus abyssinica Hochst., Rhus albida Schousboe, Rhus copallina, and Rhus coriaria L. have been utilised for tanning (Usher 1974). The fruits of certain species of Rhus L. have been used by American Indians to make a drink. Indian lemonade is prepared from Rhus typhina L.; Rhus aromatica Aiton (syns Rhus canadensis Marshall, Schmalzia aromatica Desv.), Rhus copallina, and Rhus glabra may also be utilised in this way (Usher 1974). Rhus typhina L., the stag's horn sumach, makes a quite attractive ornamental shrub and is often grown in gardens. A few other species of Rhus may be encountered more rarely, as may Cotinus coggygria Scop., the smoke tree. Plants of the family Anacardiaceae are probably the most common single cause of contact dermatitis in man. The skin reaction occurs following sensitisation to various alkyl- catechols, phenols, quinols, and resorcinols. At high concentrations, these compounds are also primary irritants. The 15 species of this genus are natives of tropical America. Some, particularly Anacardium occidentale L., are widely cultivated throughout the tropics. Leichhardt (1847) wrote: " … we also found a new tree, a species of Anacardium, which the natives called “Lugula;” it bore a red succulent fruit, formed by the enlargement of the stalk, with a greyish one-seeded nut outside, like Exocarpus. The fruit was extremely refreshing; the envelope, however, contained such an acrid juice that it ate into and discoloured my skin, and raised blisters wherever it touched it: these blisters were not only followed by a simple excoriation, but by a deep and painful ulceration."
This tree provides timber (Hausen 1981), but Woods & Calnan (1976) found no reference to dermatitis from it.
This species is a native of Brazil but is cultivated in many parts of the tropics. The tree is grown principally for its nuts, but is also important for the oil obtained from the nut shells (cashew nut shell liquid), and its gum. Its timber, known as acajou (as also is the timber of various species of Swietenia Jacq. and Khaya A.Juss. in the family Meliaceae), is used for house and boat building in South America but is not exported (Hausen 1973). Principally from studies of cashew nut shell liquid, this species has been found to be a source of a wide variety of irritant / allergenic alk(en)ylphenols. Anacardic acid (a mixture of 2-carboxy-3-alk(en)ylphenols), cardanol (a mixture of 3-alk(en)ylphenols), and cardol (a mixture of 5-alk(en)ylresorcinols), together with a series of less thoroughly investigated 2-methyl-5-alk(en)ylresorcinols may be involved as primary and secondary contact allergens, and also as primary irritants (Evans & Schmidt 1980). The bark of the tree contains a thick, resinous, acrid sap which blackens on exposure to the air. The wood exudes a yellow gum, named cashawa gum or gomme d'acajou, which can blister the skin. The yellow or red cashew apple (technically a swollen peduncle) contains a juice that is astringent until the fruit is ripe, when it is acid but edible. The apple is the receptacle of the true fruit — the cashew nut. This nut is lightly attached to the apex of the apple, and attains its full size before the receptacle enlarges to form the apple. The apple is thus a false fruit. Between the smooth outer shell and the inner shell of the nut is a fibrous pulp containing a sticky brown oil - cashew nut shell liquid. This is caustic and sensitising. The kidney shaped kernel is the cashew nut of commerce and is innocuous unless contaminated with the shell oil, in which case it will appear blackened. As with other nuts, the kernel contains a fixed oil resembling almond oil (Prunus amygdalus Batsch, fam. Rosaceae). This is termed cashew oil or anacardic oil. Ambiguity may arise between the use of the terms cashew oil and cashew nut shell liquid (Morton 1961). The distribution of irritants and sensitisers in the various parts of the tree is such that any person from the wood cutter to the consumer of cashew nuts is at risk. For the nut addict, however, the risk is indeed small. The cashew apples with nuts attached fall from the trees when ripe. The nuts are processed to obtain the kernels, together with cashew nut shell liquid as a by-product. One method involves roasting the nuts on an open fire to dispel some of the caustic oil. The fumes from such fires are irritating to the eyes, nose, throat, and skin. When roasted, the nut shells are split open and the nuts removed (Morton 1961). Mechanisation allows the nuts to be obtained from the unroasted nuts and hence increases the quantity of nut shell oil available for subsequent sale. The nut shell oil will blister the skin on contact (Morton 1958). It is used in indigenous medicine as a rubefacient and vesicant (Morton 1961). Nadkarni (1976) recorded that in Indian traditional medicine, the juice of the nut is used as a substitute for iodine locally whilst the oil obtained from the shell by maceration in spirit is applied to cracks of the feet. He also noted that the fruit is useful as an anaesthetic in leprosy and psoriasis, and as a blister in the treatment of warts, corns, and ulcers. Wren (1975) noted that the fresh juice of the shell is acrid and corrosive, and that West Indian negroes use it for warts and corns. The nut shell oil also has many industrial uses, including use in the manufacture of brake linings. It has been used as a preservative for fishing lines and as an insect repellant in book bindings. A dilute extract has been used as a gloss on vanilla pods (Vanilla Mill. species, fam. Orchidaceae), and has been held responsible for "vanilla itch" in workers handling the treated beans. Both the sap of the tree and the oil can be used for marking cloths, but are considered less of a dermatological hazard than marking nut oil from Semecarpus anacardium L. The gum is used as a varnish to protect books and woodcarvings from insects, and also as a substitute for Gum Acacia (from Senegalia senegal (L.) Britton and related species, fam. Leguminosae) in adhesives (Morton 1961). The fact that dermatitis may result from contact with cashew nut shells has undoubtedly been known for a very long time in regions where the tree grows naturally. Perhaps the earliest record is that of De Préfontaine (1763) who, referring to ACAJOU-POMME [the cashew], noted that:
Over a hundred years later, Lewin (1882) recorded a case described by Schwerin (undated) of a woman who put one half of a "bean" in her ear to relieve a toothache and pain in the face. She developed oedema of the ear, eyelid, cheek, and neck. Lewin (1882) also described a case where a "bean", divided longitudinally, was placed upon a string hung around the neck in such a manner that it lay over the manubrium sterni. Two days later, vesicular dermatitis appeared on the upper anterior trunk. Those felling the trees may suffer an irritant dermatitis (Hausen 1973); such a case has been described where the sap caused a localised lesion of the skin on a farmer's chest (Bedi 1971). An additional hazard occurs when the tree is infested with caterpillars having irritant hairs. Biting the unripe apples can cause a primary irritant dermatitis around the mouth (Bedi 1971). The cashew apple may also elicit a different reaction - Strobel et al. (1978) described a case where perioral dermatitis resembling herpes occurred in a female who had eaten an unpeeled cashew apple. The ulceration took more than 10 days to resolve. Workers on cashew nut farms may develop an acute dermatitis resembling that commonly observed in sensitised persons, but sometimes the only lesions are roughness, cracking, and irritation of fingers and hands (Behl et al. 1966, Cueva 1965). This chronic dermatitis afflicts particularly those employed in removing the kernels from roasted nuts (Morton 1961). Unprocessed nuts were responsible for dermatitis amongst dock workers who unloaded them, and also in a secretary and chemist who handled them (Downing & Gurney 1940). Roasted cashew nuts sold as ornaments or as heads of "swizzle sticks" used for stirring drinks have caused dermatitis because they had been inadequately roasted and oil had seeped through the shell (Morton 1961). Nine workmen developed dermatitis after dipping electrical equipment in a commercial varnish containing raw cashew nut shell liquid (Lockey 1944). One of the nine developed exfoliative dermatitis and severe anaemia, haematuria, and prostration. Occupational dermatitis from cashew nut shell liquid was discussed by Schwartz et al. (1945). Small amounts of the urushiol transferred from the shell to the nuts during shelling produced dermatitis when the fresh nuts were ingested in large amounts by five Toxicodendron Mill. sensitive individuals. Antigenicity disappears in a few days so that "stale" raw cashews like the commercially available dry roasted variety are harmless (Ratner et al. 1974). The occurrence of cross-sensitivity between the urushiols of poison ivy (Toxicodendron radicans Kuntze) and those of cashew nut shell liquid has long been recognised (Keil et al. 1945a, 1945b). The heartwood of this species is a minor timber of commerce (Hausen 1981). The sawdust sometimes causes such intense skin irritation that the affected areas resemble second degree burns (Freise 1932). The wood often resembles that of Dalbergia L.f. species (fam. Leguminosae) and may be mixed with shipments of them (Record & Hess 1943).
North Queensland forest officers are unanimous in stating that the wood is poisonous if rubbed on the skin (Cleland 1943). Mitchell & Maibach (1977) noted the absence of cross-sensitivity to the dried leaves of this species in patients sensitive to poison ivy (Toxicodendron Mill. spp., fam. Anacardiaceae). Three patients out of 39 tested did however show 1+ reactions to the leaves; these reactions were judged to be irritant. The genus Blepharocarya F.Muell. comprises just two species of trees found in north-eastern Australia. The genus has been classified in its own family by some authorities, namely the Blepharocaryaceae. The 25 species are natives of Indo-Malaysia and tropical Australia. Burgess (1966) states that the black sap of Buchanania species is said to be non-irritant.
The juice of Buchanania lucida was noted by a plant collector to produce itching (von Reis Altschul 1973). Some of the 15 species in this genus, which occurs throughout the tropics, are known in Malaya to produce dermatitis (Kochummen 1972). Corner (1952), referring to three species found in Malaya, states that they contain a slightly resinous sap which is harmful to some persons, especially that which oozes from the wood. The wood sap of this tree may cause dermatitis in some persons (Corner 1952, Burgess 1966). The oily exudate from this tree contains long chain alicyclic keto alcohols, together with small quantities of alkylquinols of which nonadecylquinol has been identified (Lamberton 1959a). In New Guinea, an oil (known as tigaso oil) obtained from this species has been used, sometimes mixed with soot, as an application to the body in order to give protection from lice and fleas. A long chain alicyclic keto alcohol has been isolated from the oil (Dalton & Lamberton 1958), but no urushiols. The wood of Campnosperma coriaceum (Jack) Hallier f. ex Steenis [see below] also yields tigaso oil (Hou 1978).
These species may cause dermatitis in some persons (Corner 1952, Burgess 1966).
The water extract of the bark of the tree has been used in Vietnamese traditional medicine as a remedy for second degree burns (Doanh et al. 1996). Ippen (1983) provided a case report from Germany of a female patient who had become sensitised to "poison ivy" during a visit to the USA and who, several months after her return, on patch testing with fresh leaves from a variety of species from the family Anacardiaceae, showed a strong (3+) delayed (120h) reaction to Choerospondias axillaris var. japonica (Ohwi) Ohwi. She reacted also to the leaves of Rhus copallinum L., Rhus javanica L., and Toxicodendron trichocarpum Kuntze, and to the flesh and peel of mango (Mangifera indica L.). The 20 species are natives of Central America and the West Indies. Oviedo reported (Standley 1927) that the Indian women of Santo Domingo used a vesicant paste made of the roots of Comocladia species to soften and lighten the skin of their arms and faces. In 1845, Williams (1845/46) drew attention to a report by Otto in the Gardeners Magazine of May 1842 of intensely severe oedema after minimal contact with the irritant sap of Comocladia species. Dahlgren & Standley (1944) note that the sap of some species causes blistering and prolonged inflammation similar to that caused by poison ivy (Toxicodendron radicans Kuntze) whilst Pardo-Castello (1933) notes that at least 17 of the 20 species are said to be capable of producing dermatitis. This species is among the 14 most common causes of plant contact dermatitis in the Dominican Republic (Brache & Aquino 1978). Lunin (1969) has also observed very many cases of dermatitis from this species on the steppes of Russia. The timber, known as bastard brazil, is used locally for general purposes and can cause dermatitis (Standley 1927, Schwartz et al. 1957). The dermatitis may be persistent as the resin contaminates clothing and tools (Pardo-Castello 1962). Oakes & Butcher (1962) note that this species has spiny leaves that can cause mechanical injury, and also sap that can produce severe dermatitis. It is among the 14 most common causes of plant contact dermatitis in the Dominican Republic (Brache & Aquino 1978). This species are able to produce dermatitis (Brache & Aquino 1978). von Reis Altschul (1973) found an herbarium note stating that the milky juice causes poison ivy-like dermatitis. von Reis Altschul (1973) found an herbarium note stating that Comocladia engleriana contains a thick irritating juice … persons often being affecting just by passing the tree.
This species and its varieties are occasionally grown as ornamental shrubs for their brilliant leaf colouring in autumn (fall). The species occurs naturally from the Mediterranean to China. The wood, when cut for veneers, and the sap have both been reported to cause dermatitis (Hausen 1970, Behl et al. 1966). A yellow dye ("young fustic") may be obtained from the wood (Remington et al. 1918). The leaves were formerly used for tanning because of their high tannin content (Hurst 1942).
This species is often referred to as Dracontomelum dao, a name of no botanical standing. It is the source of a timber that is used commercially for veneers and in the manufacture of fine furniture. No reports of ill effects in those who are exposed to the timber or its sawdust have been found. Perry & Metzger (1980) note that in China, the fruit of this species is given as a depurative to cure dermatitis. A recent study of the genera Gluta and Melanorrhoea Wall. by Hou (1978) has resulted in the proposal that the whole of the genus Melanorrhoea be reduced to Gluta. The new enlarged genus thus contains about 30 species distributed in Madagascar, India, Burma, Thailand, Indochina, China, and throughout Malesia but not (yet) in the Philippines (Hou 1978). Various vernacular names — rengas (Malaya), hangus (Penang), rangus (Sakar), ruengas (Sudan), ingas (Indonesia), angas and ligas (Philippines) — are applied to trees the sap of which produces sores of the skin. The species concerned are mainly in the genus Gluta; their white irritant sap turns black on exposure to the air (Burkill 1935), a feature commonly found in the Anacardiaceae (Hou 1978). In Malaya, the more poisonous kinds are usually called kerbau jalung — the untamed buffalo — as are some species of Melanochyla Hook.f. It is unwise even to sit beneath these, for raindrops carry down the poison from the leaves (Corner 1952). Many provide hard, durable, beautifully marked timber, the heartwood often being blood-red in colour. However, the irritancy of the sap limits its value. In the timber trade, the term rengas or renghas is reserved for the red heartwood of Gluta species. The terms Singapore mahogany and Straits mahogany may also refer to timber from Gluta species. Only a few species are regularly distributed by the timber trade (Hausen 1973). It is excellent material for furniture and turning, and is used in Malaya for making "daching" — Chinese weighing scales. However, even thoroughly seasoned timber, furniture, etc. may affect allergically sensitised persons. The black sap tends to find its way through polish, but a further application of polish, particularly a modern polyurethane lacquer, after two or three years is likely to alleviate the problem (Burgess 1966). Rengas poisoning in the form of acute dermatitis with constitutional symptoms is not uncommon in Malaya in estate labourers, gardeners, and wood cutters (Gimlette 1929, Samuel 1935). Contact not only with the fresh sap, but also with branches that have been cut and dried for months can produce the sores (Hornsey 1914). Corner (1952) noted that Gluta species have been inadequately collected because the irritant sap deters plant collectors seeking material for herbaria. In the last century, Upwich (1894) described dermatitis that occurred in two companies of soldiers after they waded in a river on the banks of which were growing rengas trees whose fruits had contaminated the river. Noosten & Visser (1936) also noted that the fruit juice can cause dermatitis.
According to Burgess (1966), both species have irritant sap, but Halim et al. (1980) could not detect urushiols in an extract of the bark of Melanorrhoea beccarii. The sap causes dermatitis (Brown 1891, Matthes & Schreiber 1914, Senear 1933, Corner 1952). A scantily clad person who scrambles through the broken branches may suffer a widespread dermatitis, which may be complicated by fever and other constitutional symptoms, and has occasionally proved fatal (Burkill 1935). The sap causes dermatitis (Burkill 1935, Corner 1952). The milky juice is caustic (Perry & Metzger 1980). Bertrand & Brooks (1934) isolated from this species a phenolic compound which they named moréacol. Although the structure of this compound has not been confirmed, Backer & Haack (1941a) believed moréacol to be identical with thitsiol, an urushiol from Gluta usitata Ding Hou. This species is a source of a lacquer, named camboge lacquer, in Indochina (see also G. usitata).
This species has been reported to be irritant (Corner 1952).
The timber of this large river-side tree is beautifully marked, but has a sinister reputation amongst forestry workers (Foxworthy 1927, Lewin 1928, Grevenstuk 1937). However, it is used for building, for boats, for furniture, and for inlay work (Hausen 1973). Gimlette (1929) described the sap as irritant. Those employed in felling the trees may develop an acute vesicular dermatitis (Ridley 1922). A chair made from the wood of this species has caused dermatitis of the legs (Hausen 1973). The poisonous character of G. renghas was known to Rumphius (Herb. Amboin. ii. 259, t. 86; 1750): "The exhalations of this tree are considered noxious, and the people of Macassar and other parts of Celebes in particular, entertain such dread of it, that they dare not remain long under it, much less repose beneath its shade; they say that whoever receives the droppings from it will have his body swell and be affected with malignant sores". "Not only are the fruit, leaves, and twigs of the Rengas trees (species of Gluta and Melanorrhoea) poisonous, but the timber also, even after long keeping, is apt to produce injury. Dr. Brown says that he was informed that after years of seasoning, when the wood is cut up, it gives rise to painful and intractable eruptions on the hands and bodies of the workmen. The timber is a very handsome red wood, streaked more or less with black, and was formerly known as Singapore Mahogany and much valued as a cabinet wood or for buildings. The Kedah Malays, on felling a tree, would leave it lying in the forest till the bark and sap-wood was rotted away or removed by termites, after which they said it was safe to move. As a furniture wood, however, it went out of fashion, as even after being made up it was said to seriously affect many persons living in the room with it, producing great irritation of the mouth, nose and throat, especially when it began to get old, worn-out and dusty" (Ridley 1911, cited by Sprague 1921). The vesicant latex of this species has been found to contain an incompletely characterised 3-heptadecenylcatechol, which was named glutarenghol (Backer & Haack 1941a). Burgess (1966) reports that this species is irritant.
The sap of both of these species is irritant (Thiébault 1965). This species is the source of lacquer in Burma. The tree is tapped by making V-shaped cuts with a chisel. The bark above each cut is torn to produce a cavity into which is inserted a shoot of bamboo with an obliquely cut mouth, to form a spout. The latex, which at first is yellow-white, turns black but remains fluid. It is stored in jars for distribution. It can be used as a varnish or, after mixing with ashes, sawdust, or similar material, it can be moulded. For ornamental use, it may be coloured by the addition of pigment. The varnish is used on umbrellas, to give a surface to trays, on drinking cups and similar articles, and as a cement for Burmese glass ceramics (Watt 1906, Burkill 1935). The timber from this species is known in the trade as varnish tree or mai leek. It is hard, durable, and finely marked; it is used for furniture, inlay work, and the like (Hausen 1973). The sap may splash the skin whilst the trees are being felled, producing much irritation, hence wood cutters object to fell the tree (Watt 1906). The sawdust of trees felled three or four years earlier, and even old furniture, may cause dermatitis and irritation of the mouth nose and throat (Watt 1891, Schwartz et al. 1957, Behl et al. 1966). According to Nadkarni (1976), the oleoresin of this species is used in Burma in combination with honey as an anthelmintic in skin diseases. If it be too much handled it causes erysipelas-like swellings among some, which are cured by applying an infusion of teak wood. An incompletely identified 4-heptadec(en)ylcatechol, which was named thitsiol, has been reported to occur in this species (Majima 1922b). The wood causes dermatitis; the fruit and leaves are also poisonous and have been used for criminal purposes (Ridley 1911, 1922, Corner 1952). The dried wood and sap both retain their dermatitic properties (Burkill 1935). This species can produce dermatitis (Gimlette 1929).
The beautifully coloured wood is used in furniture, and is one of the timbers known in the trade as rengas. It has so far been imported to Europe only as samples (Hausen 1973). Felled trees are commonly left in the jungle for the sapwood to be destroyed by decay and by white ants (termites), after which they are considered safe to move. The sap causes dermatitis (Ridley 1911, 1922, Matthes & Schreiber 1914, Lewin 1928, Senear 1933, Corner 1952, Schwartz et al. 1957, Thiébault 1965, Burgess 1966, Behl et al. 1966). This species is said to be the most virulent of the rengas (Ridley 1911, 1922, Burkill 1935). The timber is beautifully marked.
The genus Heeria Meisn. is monotypic, forming an evergreen tree that is found growing naturally in the southwestern Cape region of South Africa. According to Von Teichman & Van Wyk (1996), the gum exudate from the bark has been used as an ointment to draw boils and abscesses. This species has been reported by Ross (1959) to have caused severe dermatitis in Pondoland. However, the Curator of the Pretoria Botanical Gardens has not seen reactions to the plant in visitors who had handled it. This species contains a black, very acrid oleoresin, the powerfully vesicant properties of which are dreaded by local people (Behl et al. 1966). Not all persons coming into contact with the sap develop dermatitis (Chopra et al. 1949), suggesting allergenicity rather than irritancy. The fixed oil of the seed kernel has been found to contain laccol, identified as 3-n-heptadecadienylcatechol (Nair et al. 1952a).
These species have properties similar to those of H. arnottiana. The black varnish obtained from H. longifolia is caustic and vesicant (Chopra et al. 1949). The tree has so evil a reputation (because of its irritant sap) that it can hardly be felled (Watt 1906). About 70 species are native to tropical Africa, and one to Indomalaysia. Some of the African species yield timber that is used locally; others are employed for a variety of purposes in indigenous medicine (Watt & Breyer-Brandwijk 1962). This East Indian member of the genus is strongly irritant (Verbunt 1933). The timber, known in the trade as aroeira or pao bugre, is used for posts and fences, and sometimes for furniture. The sap is powerfully irritant (Mors & Rizzini 1961) and severe dermatitis has resulted from contact with the timber (Hausen 1981). The timber, known in the trade as aroeira [see also Lithraea brasiliensis Marchand above] or litre, is used in Brazil and Chile for cabinet work. Severe dermatitis has resulted from contact with the wood (Hausen 1970, 1981), although according to Webster (1911) the dried wood is said to be harmless. Cross-sensitivity to Rhus L. (Toxicodendron Mill.), Mauria Kunth, and other members of the Anacardiaceae was investigated by Oliveira Lima (1953) and Hurtado (1968). Barham (1794) referred to swelling of the face and body from sleeping under the tree. The sap and, at certain times of the year, the exudate from the leaves is highly irritant (Sprague 1921): Feuillée, who visited South America in 1702–12, related that some of the seamen of his ship suffered severely as the result of cutting down some "Llithi" trees (Lithraea caustica) on the coast of Chile. By the following day, their heads had swollen to an extraordinary size, and their features had become indistinguishable; they might have been taken for monsters rather than men (Obs. ii. 33, t.25, fig. dextra; 1725). According to Molina (Hist., Engl. ed. 144; 1809), "the effluvium from this tree, especially in summer, produces painful pustules and swellings on the hands and faces of those who stop beneath its shade. This effect is various, however, with various persons: there are some who are very little, if at all, incommoded by it, while others, who merely pass by the tree, are severely affected; though never attended with fatal consequences, it is, nevertheless, very troublesome. Great precaution is requisite in cutting the tree, as its viscous juice is extremely caustic; but when dry, the wood loses all its injurious qualities". Molina, who has been described as "one of the most pernicious blunderers who have brought confusion into Natural History" (J. Ball, Notes Nat. S. Am. 175; 1887) is not very trustworthy; but, according to Gillies, "the statement made by Molina, relative to the poisonous nature of this tree, seems to be well founded; as I am informed, by several intelligent people, that individuals resting or sleeping under it at certain times of the year, are afterwards attacked with eruptions all over the body" (Hook. & Arn. Bot. Beechey's Voy. 16; 1832). Gay (Fl. Chil. ii. 44; 1846) stated that the "Liti" or "Litre" tree (Lithraea caustica) is common on hills and sun-exposed plains in central Chile, extending from Coquimbo to Arauco; and that the danger of remaining underneath it or of burning it is well known. It is mostly women, children, and persons of weak constitution who are affected. The oleoresin from this species has been used to induce allergic contact dermatitis in guinea pigs (Oliveira Lima 1953). Contact with the leaves can cause dermatitis but the wood does not seem to be irritant (Paulson 1942). The 40 species were originally natives of south-eastern Asia and Indomalaysia, but many are now cultivated or have become naturalised in tropical regions throughout the world because of their importance as sources of food and timber. Inconsistency in the use of trade names is particularly confusing in this genus. The term asam is commonly applied to these timbers; the coloured heartwood present in some species is referred to as figured asam. Unfortunately, the term asam is applied also to timbers derived from members of the family Burseraceae, notably species of Canarium L., Dacryodes Vahl, Santiria Blume, Scutinanthe Thwaites, and Triomma Hook.f. The identity of material from some Mangifera species is in doubt, as the genus awaits botanical revision (Burgess 1966). The following are grown commercially for timber: Mangifera caesia Jack, Mangifera foetida Lour., Mangifera indica L., Mangifera macrocarpa Blume, Mangifera odorata Griffith, Mangifera pajang Kosterm., and Mangifera quadrifida Jack. This species is grown for its timber and to some extent for its fruit, although the foetid odour of the fruit reduces its palatability (Corner 1952). Eating the fruit may cause dermatitis localised to the angles of the mouth (Simmons & Bolin 1921), or stomatitis, being caused by contamination of the fruit with plant sap. The fruit pulp is innocuous (Fasal 1945). The sap of the fully grown tree is irritant and has been used for criminal purposes. Raindrops contaminated by bruised foliage may irritate the skin. The smoke from burning foliage or wood is unpleasantly acrid (Burkill 1935) and may cause dermatitis in those exposed to it (Simmons & Bolin 1921, Landor 1943). The mango is extensively cultivated throughout the tropics, and there are a large number of varieties to be found, differing in the quality of their fruit and timber. Varieties do not reliably reproduce their qualities in their seedlings and are therefore propagated vegetatively, often being grafted onto Mangifera foetida rootstock. The fruit is widely consumed in the tropics, some being exported to temperate regions. Chutneys are made from unripe mangoes; very young leaves and flowers may also be eaten. The leaves are sometimes fed to cattle in times of scarcity. The timber, sold under the trade name of amba, is used locally for boat building and furniture, but is not exported (Hausen 1973). Another trade name for the timber is aruba, and there are a number of local names in current use: machang (Malaya and Sarawak), sepam (Malaya), mango or mangga (India and Pakistan), xoai (Vietnam), and membatjang (Indonesia). Allen (1943) noted that the growing plant itself and many of the commercial products derived from it are potential causes of dermatitis; and that handling the green fruits or breaking the branches may result in dermatitis, as may contact with windblown pollen. Morton (1969, 1971) cautioned that the tree is a major cause of widespread respiratory difficulty when in bloom. However, according to Lakhanpal & Nair (1958), mango pollen is not anemophilous. Contact with the wood or its sawdust may cause dermatitis (Simmons & Bolin 1921). Dermatitis of irregular distribution may occur in children climbing the trees. The most commonly observed clinical syndrome of mango dermatitis follows peeling and eating the fruit. The face, especially around the mouth, is most severely involved (Nasution et al. 1973), but the irritant may be carried by the fingers to the neck. Some dermatitis of the hands is not unusual (Kirby-Smith 1938). The linear vesicles of poison ivy (Toxicodendron Mill. species) dermatitis are not a feature. Allergenic material is found in stems, leaves, and pericarp (peel), but not in the fruit juice which may be drunk with impunity by sensitised persons (Behl et al. 1966). Zakon (1939) obtained a positive patch test reaction to the peel in one case of facial dermatitis. Goldberg (1954) reported two cases of facial dermatitis that followed peeling and eating mangoes, but patch tests were not carried out. In other cases (Brown & Brown 1941) patch tests were positive to an oil extracted from the peel, but not to the pulp of the fruit. The fruit may be eaten safely by sensitised persons provided all contact with the peel or the stem can be avoided (Keil et al. 1946). During harvesting of the fruit, stem sap may contaminate the peel which then shows bleached, varnished, or blackened patches. This dried sap may cause dermatitis localised to the angles of the mouth (Simmons & Bolin 1921), or stomatitis (Fasal 1945). A reaction of a different type occurs more rarely. Contact with the peel may cause urticarial whealing (Behl et al. 1966) and asthma (Kahn 1942). Urticaria alone or with shock has been reported after eating mangoes (Lindenbaum 1962, Lindenbaum 1963, Rubin et al. 1965, Dang & Bell 1967). Dermatitis from the mango occurs wherever this tree is grown. During its fruiting season in Hawai‘i, it is the predominant cause of dermatitis from plants (Arnold 1972). Mango dermatitis has been reported from the Philippines (Gibson & Concepción 1914, Concepción 1914), from Argentina (Silva 1945), the Dutch West Indies (Tillema 1936), Florida (Blank 1957), as well as from the East Indies and Japan (Asai 1939). Patch tests carried out using the leaves of the mango crushed in a small quantity of normal saline elicited a positive reaction in 1 of 10 contact dermatitis patients tested in New Delhi, India (Singh et al. 1978). Mango appears to be a less powerful primary sensitiser than poison ivy (Toxicodendron species). North Americans already sensitised to poison ivy are more likely to develop mango dermatitis than are the inhabitants of mango-growing regions (Blank 1957). Previous clinical or subclinical sensitivity to other anacardiaceous species will also influence the incidence of mango dermatitis. It seems probable that varieties of mango differ in their allergenic potential (Blohm 1962). The evidence for racial as distinct from environmental influences on the incidence of dermatitis is not conclusive. Although the chemical nature of the allergenic material in mangoes has not been studied, cross-sensitivity has been demonstrated to poison ivy in man (Keil et al. 1946) and to 3-pentadecylcatechol in guinea pigs (Wechsler 1960). Senear (1933), Burkill (1935), and Schwartz et al. (1957) noted that the resin from this species is injurious to the skin of wood cutters. The vapour from freshly bruised tissues, the smoke from a bonfire of the leaves, or raindrops from the crown of the tree may affect the skin (Corner 1952). Although the fruit is inferior to that of M. indica, this tree is extensively cultivated for its fruit in Malaya because it is more easily grown there. The sap of the bark is irritant (Burkill 1935) but it is chiefly the sap of the unripe fruit that causes skin reactions (Corner 1952). The fruit, depending on variety, may have a strong turpentine-like smell. Known as sapian mango in Guam, the plant is also reported by Souder (1963) and Ridley (1922) to cause dermatitis. Hou (1978) believes that Mangifera odorata is of hybrid origin: Mangifera foetida × Mangifera indica. It is very variable and apparently includes many forms of a hybrid swarm. This species is said by the natives to be poisonous. The plant can cause dermatitis (Triana 1872). According to an herbarium note found by von Reis Altschul (1973), this species produces skin eruptions in some persons. Cross-sensitivity in humans was observed between this plant, Toxicodendron Mill. species, and Lithraea caustica Hook. & Arn. Experiments in guinea pigs showed that an extract of the tree bark has sensitising properties and that cross-sensitivity to 3-n-pentadecylcatechol occurs (Hurtado et al. 1982, Hurtado 1968). The 12 species are natives of western Malaysia. Together with species from other genera (see Gluta and Parishia), they are often called rengas trees. This uncommon tree is not usually cut because of its irritant sap (Corner 1952, Burgess 1966) which is known to cause dermatitis (Senear 1933, Schwartz et al. 1957).
These two species are reported to cause skin reactions (Corner 1952)?. The three species are natives of the West Indies, Florida, and Mexico. The genus was at one time classified in the family Spondiaceae (or Spondiadaceae). Holiday-makers from British Columbia visiting the Caribbean have developed dermatitis after their return home from contact with Metopium species during their holiday (Mitchell JC 1979 — unpublished observation). The timber, known as black poison wood, is used locally for general purposes (Hausen 1973). The sap can cause painful irritation of the skin (Pardo-Castello 1923, Standley 1927, Baumer 1955).
The tree is widely distributed in Florida (Morton 1971) and in the Caribbean region (Kingsbury 1964). Both the sap of the plant and its fruit are irritant (Weber 1937, Simons 1953, Usher 1974). According to Morton (1958), contact with any part of the tree, and especially with the clear, sticky sap which turns black on exposure to the air, can produce any degree of dermatitis from a mild rash to large blisters which spread from one part of the body to another. The smoke from the burning wood is as dangerous as the sap (Dahlgren & Standley 1944). The sap of Rhus metopium L. in Jamaica is pale yellow but changes to a deep brown colour on the skin. Lifting and carrying the branches on the shoulders caused vesicular dermatitis of the hands, neck, and shoulders (Grabham 1899). When used in wreaths and bouquets, the plant can cause dermatitis; it may also do so if overhanging branches brush against clothes hanging on a line (Morton 1971). An outbreak of dermatitis occurred among Air Force personnel clearing undergrowth in the Bahamas, and in residents incautiously gathering trees for Christmas (Jackson 1946). In a subsequent clinical investigation involving 20 volunteers, the juice from under the bark, when applied to the skin, produced local vesiculation and erythema. Twelve subjects reacted only locally; one subject developed a generalised spreading rash; six were unaffected. Jackson himself experienced itching a few minutes after application of the bark juice. This developed into a small papule by the next day and superficial ulceration after four days with resolution starting after seven days. The berry juice tested on himself seemed to be more virulent, causing a widespread erythematous vesicular eruption that lasted for several weeks. Lunin (1969) observed patients with dermatitis from Metopium toxiferum in Russia. Brown et al. (1973) also reported contact dermatitis from this species. The stem yields a resin (doctor's gum, hog gum) which has been used as a violent purgative; the wood has been used to adulterate Quassia amara L. (Usher 1974). Metopium toxiferum has been reported to contain a mixture of 3-n-pentadec(en)yl and 3-n-heptadec(en)ylcatechols (Gross et al. 1975).
Hitch (1944), referring to Semecarpus atra, and King (1966), referring to Semecarpus vitiensis, state that the irritant milky juice may cause dermatitis. However, Halim et al. (1980) could not detect the presence of urushiols in a chloroform extract of the heartwood of this species. Twelve species are found in Burma and western Malaysia. The timber from some species, which may be known as rengas (see also Gluta, Melanochyla, and Semecarpus), has been used for fine furniture and ornamental work. It can cause dermatitis (Senear 1933). The five species occur in Malaysia and the Solomon Islands. According to Corner (1952), the sap of Pentaspadon species in general is not dermatitic and indeed the oil from some species is used in Malaya for treating skin diseases. An incompletely characterised 2-carboxy-3-heptadecadienylphenol named pelandjauic acid has been reported from this species (Backer & Haack 1941b). The oil from the wood consists largely of 2-carboxy-3-heptadecadienylphenol, and is very similar to the oil from P. motleyi (Lamberton 1959b). According to Burkill (1935), the oleoresin is black and greatly irritant to the skin. This species can produce dermatitis (Von Humboldt et al. 1825). The plant was listed as irritant by Pammel (1911). According to an herbarium note found by von Reis Altschul (1973), the sap and wood are acrid causing skin eruptions. There are over 200 species widely distributed over subtropical and warm temperate regions. Many species formerly considered to belong to the genus Rhus are now placed in the genus Toxicodendron Mill. (see Gillis 1971). Toxicodendron now includes most of the more virulently dermatitic species such as poison ivy and poison oak, even though the reclassification was carried out on morphological rather than chemical grounds. According to Chopra et al. (1949), many Rhus species cause dermatitis. Some Indian villagers have an almost superstitious dread of all species; they believe that the smoke from the burning wood can cause swelling and vesication of the skin. (Since the genus Toxicodendron occurs in eastern Asia as well as in North America, it is likely that some of the Rhus species referred to by Chopra et al. were actually Toxicodendron species). Species of Rhus are commonly referred to as sumachs or sumacs. Sumac dermatitis in Russia was reviewed by Gorbovitski et al. (1974).
This plant, a native of China and Japan, provides Chinese (or Japanese) nutgalls – also known as wu pei tzu, wu bei zi, or Galla Sinensis (五倍子) – which grow on the leaves and leaf stalks in response to the activities of certain insects (Chinese sumac aphids: Schlechtendalia chinensis Bell, fam. Aphididae). These galls are rich in tannins. In traditional Chinese medicine, they are used in topical applications to chancres, swellings and wounds (Stuart 1911). The residue obtained in the factory production of tannin from an ethereal extract of "Galläpfeln" was found to contain a substance named cyclogallipharic acid (Kunz-Krause 1904). The title of Schelle's dissertation from Basel University in 1903, in which the work was originally described, later to be formally published in 1904, was entitled: "Beitrage zur Kenntnis der chemischen Bestandteile der Eichengallen. Ueber die Cyklogallipharsäure, eine neue, in den Galläpfeln vorkommende, cyklische Fettsäure" (see Kunz-Krause & Schelle 1904). This appears to refer to galls obtained from oak species ("Eichengallen"), otherwise known as Aleppo galls (found on Quercus infectoria G.Olivier fam. Fagaceae — see Trease & Evans 1966). It is likely that Schelle's work was actually – perhaps unwittingly – carried out on Chinese galls ("chinesischen Galläpfeln") found on Rhus chinensis. Indeed, Kawamura (1928) referred to "japanischen Galläpfeln" as the botanical source of the cyclogallipharic acid that Kunz-Krause & Schelle had isolated. He also reported that cyclogallipharic acid, upon decarboxylation, produced cyclogallipharol, an alkylphenol that was identical with hydroginkgol derived from Ginkgo biloba L. (fam. Ginkgoaceae). And he established that hydroginkgol was, structurally, 3-pentadecylphenol (see also Loev & Dawson 1958). It follows that cyclogallipharic acid, although only incompletely characterised by Kunz-Krause & Schelle (1904) is, structurally, 6-pentadecylsalicylic acid, a member of a class of alk(en)yl salicylic acids known collectively as anacardic acids. Bagchi et al. (1985) subsequently reported the isolation and characterisation of 6-pentadecylsalicylic acid from a petrol extract of the leaves of Rhus semialata. Whilst 6-pentadecenylsalicylic acid has been shown to be a sensitiser in guinea pigs (Lepoittevin et al. 1989, Hausen 1998), the saturated side-chain analogue 6-pentadecylsalicylic acid showed no activity as an elicitor on guinea pigs sensitised to unsaturated side-chain analogues of anacardic acid from Ginkgo biloba L. (fam. Ginkgoaceae).
Kuo et al. (1991) reported the isolation and characterisation of 6-pentadecylsalicylic acid from a n-hexane extract of the stems of Rhus semialata var. roxburghii. Whilst 6-pentadecenylsalicylic acid (a member of a class of alk(en)yl salicylic acids known collectively as anacardic acids) has been shown to be a sensitiser in guinea pigs (Lepoittevin et al. 1989, Hausen 1998), the saturated side-chain analogue 6-pentadecylsalicylic acid showed no activity as an elicitor on guinea pigs sensitised to unsaturated side-chain analogues of anacardic acid from Ginkgo biloba L. (fam. Ginkgoaceae). According to Anon (1908), and repeated by (Maiden 1909), Rhus coriaria "… is unquestionably dangerous and produces an erysipelas-like affection of the skin of persons who gather the leaves for the sake of the tannin they contain." The species is found in the Mediterranean region and Asia Minor. Its young branches are used in the tanning of Moroccan leather (Polunin 1969). This eastern North American species is said to cause dermatitis (Pardo-Castello 1923). The leaves, fruit, and bark of this species, which grows in Assam, can produce dermatitis; the sap is vesicant (Behl et al. 1966). The smoke from the burning wood has been reported to cause dermatitis (Watt & Breyer-Brandwijk 1962). The resin is used as a depilatory by girls among the Mikea hunter-gatherers of Madagascar (Stiles 1998). The leaves, bark, fruit, and sap can produce dermatitis (Behl et al. 1966). The plant is found in central and western China, and in the Himalayas. A scratch or prick from the sharp point of a twig (the plant has no thorns) is extremely painful and burns like fire, hence the specific epithet (Watt & Breyer-Brandwijk 1962). The wood of this species, which is found in the South Pacific, is used to make canoes in Samoa (Usher 1974). This native plant of Guam can produce dermatitis (Souder 1963). This ornamental tree is a native of North America but is widely cultivated elsewhere. Its yellow wood is soft and light, and is used for inlays (Hausen 1970). It is recorded as causing dermatitis (Großmann 1910). The leaves are said to contain irritating sap (Lindemark 1971). However, patch tests with the leaves produced no reactions on 50 consecutive eczema patients in Denmark, but did produce a strongly positive reaction in one of ten subjects in the US known to be sensitive to poison oak (Toxicodendron diversilobum Greene) (Maibach & Hjorth 1973). Ross (1974) observed a case of contact dermatitis from R. typhina in Newfoundland. The wood of this Himalayan species is used for tool handles and musical instruments. The wax from the fruit is used to make candles, and a varnish is extracted from the trunk (Usher 1974). According to Behl et al. (1966), this small tree is very closely allied to the Japanese lacquer tree (Toxicodendron vernicifluum F.A.Barkley, syn. Rhus verniciflua Stokes) and possesses similar properties. Nadkarni (1976) records that the juice of the leaves is corrosive. The seven species in this genus are confined to South America. The timber of Schinopsis balansae Engl., known as quebracho, may be found in commerce (Hausen 1981).
This tree yields a timber that is useful for building and constructional work (Hausen 1970). It has been listed as irritant by Schwartz et al. (1957) and Orsler (1973). Contact with branches, leaves or sawdust may provoke dermatitis in sensitive persons (Di Lullo 1928) and the condition is sufficiently common to have acquired the vernacular name of "mal de quebracho". The diagnosis may be confirmed by patch testing with an alcoholic extract or with an aqueous distillate (Di Lullo 1934). The dermatitic agent in this species appears not to have been identified, but Di Lullo (1934) suggests that a substance similar to cardol (see Anacardium occidentale) is responsible. He showed that sensitisation was involved since only a proportion of those exposed developed dermatitis, and this only after a latent period. This species has been implicated as a cause of phytophotodermatitis (Pathak 1974). The 30 species are native to northern and central South America, Central America, and Mexico. Some are cultivated as ornamental or shade trees wherever the climate is suitable. The aroeira sickness was described by von Bassewitz (1928). This author established that up to 10% of the population of southern Brazil has some degree of hypersensitivity to the aroeira tree. Those who were sensitive reacted not only to the tree itself, but also to dry, seasoned wood such as furniture that has been in use for some time. Unfortunately, the botanical identity of the aroeira has not been established. Von Bassewitz (1928) and Freise (1932) thought that aroeira was a species of Schinus. The timber from S. molle L. is known as aroeira, and a synonym of S. terebinthifolius Raddi is S. aroeira Vell. The term aroeira is also used for the timber from Astronium Jacq. and Lithraea Miers species. Hausen (1981) notes that the timber of both Lithraea brasiliensis Marchand and Lithraea caustica Hook. & Arn. is called aroeira. Aroeira may also refer to Lithraea aroeirinha Marchand. It is probable that the term aroeira as used in South America for species of Astronium, Lithraea, and Schinus is used as loosely as is the term rengas in Malaya for species of Gluta, Melanochyla, Parishia, and Semecarpus. Aroeira, the durable timber of this species and probably of related species, is used for bridge construction and fencing (Hausen 1973). The resin of the tree is a source of American mastic. Watt & Breyer-Brandwijk (1962) note that the leaf and bark have been used as a local application to wounds and sores. If ingested, the fruit can cause gastro-intestinal inflammation and haemorrhoids (Ruiz 1940), but has been used as a substitute for black pepper (Piper nigrum L., fam. Piperaceae) in Latin America, and northern and southern Africa (Morton 1976). A fragrance raw material known as schinus molle oil is the essential oil prepared by steam distillation of the green or ripe fruits of this species. Its principal constituents are pinene, phellandrene, and carvacrol. When applied undiluted to the skin of mice and swine, it was found to be non-irritant. However, when applied to rabbit skin under occlusion for 24 hours, it was found to be moderately irritant. The undiluted oil showed no phototoxicity to mice nor swine, and when applied at a concentration of 4% in petrolatum to the skin of 25 human volunteers, no sensitisation could be induced (Opdyke 1976). Dermatitis resembling poison ivy (Toxicodendron Mill. sp.) dermatitis occurs in those who become sensitised to the tree, its timber, or its sawdust. According to Hausen (1970), the dermatitis is likely to be caused by a phenolic substance, but no clinical investigations have been published.
Aplin (1966) noted that this species can produce skin ailments. Dermatitis as well as eye-inflammation and facial swelling are common complaints of those who trim the tree when it is in bloom or those who repeatedly trim a non-blooming hedge of this species. Crushed berries from sprays used for indoor decoration have caused severe respiratory irritation. […] children who play beneath the tree or climb it [may] suddenly exhibit symptoms usually associated with head colds or the early stages of "flu." (Morton 1969). Direct contact with the exudate from the trunk causes vesication and severe itching, the lesions resembling second-degree burns. It is also recorded that the resinous exhalation from the tree causes skin eruptions resembling those of measles or scarlet fever. This may be observed in persons resting under the tree, and in persons engaged in felling, trimming, or pruning the branches, especially while the plant is in bloom (Morton 1978a). According to an herbarium note found by von Reis Altschul (1973), the foliage causes skin irritation. The plant was listed as irritant by Pammel (1911). Some 50 species are native to Indo-Malaysia, Micronesia, and the Solomon Islands. The young fruit of most, perhaps all, species yields an irritant resin which can be used as a marking ink. Some of the species are rare and not well studied (Corner 1952). von Reis Altschul (1973) found herbarium notes on two unidentified Semecarpus species, one from Sumatra and one from Borneo, noting that the juice produced itching and burning of the skin.
This East Indian tree is used locally as a source of timber (Hausen 1973). The fruit of the tree is a nut which contains an edible kernel. The pedicel, which swells under the nut to form a false fruit, is also edible when ripe. The pericarp of the nut yields a black tarry oil known as bhilawan oil which, when mixed with lime-water or alum, has been used in India and Malaya as a marking ink. The ink is insoluble in water but soluble in alcohol (Burkill 1935). Preparations of the nut were used in ancient medicine and still find a place in indigenous medicine. Trade in the bhilawa nut is very ancient, for this fruit was the "golden acorn" of Galen (A.D. 130 - c.200) and Avicenna (d. 1037). It was estimated in 1946 that the crop consisted of about 50,000 tons of nuts containing some 20% bhilawan oil (King 1957). Marking nuts enter into the composition of some caustic paints for application to warts and piles. The powerful irritant properties of the juice of the pericarp have frequently been made use of by malingerers in producing ophthalmia and skin lesions, and also in procuring abortions (Nadkarni 1976). Dermatitis occurs in those preparing the oil, or in those applying it to clothing in their capacity as launderymen (called dhobis in India), or in those wearing the marked clothing. The term dhobi itch has been confusingly applied to both marking ink dermatitis and to tinea cruris (a ringworm infection of the groin). Dermatitis may also be caused by contact with the timber (Hausen 1973). There are two principal patterns of dermatitis (Behl et al. 1966). Those who use nut preparations medicinally may develop dermatitis of the hands and face. If the nuts are ground with a pestle in a mortar held between the knees, the legs and feet may also be affected. The second clinical pattern involves those who wear the marked clothing. Fifty two American soldiers serving in India were affected - about 14% of those exposed (Fitz-Hugh et al. 1943, Livingood et al. 1943). Indians appear to be less susceptible than Americans, but the difference is probably environmental and could be related to the previous exposure of the latter to poison ivy (Toxicodendron Mill. sp.) or of the former to the relatively weaker sensitising potential of the mango (Mangifera indica L.) (Blank 1957). Since the dhobi is accustomed to mark the inside of the shirt collar, brassière, belt, vest, or underpants, the site of the localised dermatitis tends to be the back of the neck or lower back in men, or the mid or lower back in women. As the resin is not destroyed by boiling, the mark may continue to provoke dermatitis for the life of the garment (Fasal 1945). To prevent recurrence, the mark must therefore be cut out or covered with adhesive plaster. Extensive dermatitis occurred in a girl who accidentally contaminated her skin while marking her brother's clothing with pure bhilawa juice (Behl et al. 1966). Contamination of mail by a bottle of bhilawan oil contained in the sack caused dermatitis in 16 of 50 workers sorting mail (Goldsmith 1943). A laboratory worker cutting sections of the fruit developed severe dermatitis (Fox 1921). The black corrosive liquid obtained from the pericarp of the nut is also known as bhilawa nut shell liquid, and is analogous in many respects with cashew nut shell liquid (CNSL) from Anacardium occidentale L. It has been shown by Chattopadhyaya & Khare (1969) to contain anacardic acid (probably a mixture of 2-carboxy-3-alkylphenols), but the finer structural details have not been elucidated. The major constituent of the oil is bhilawanol, a mixture of 3-n-pentadec(en)ylcatechols (Rao et al. 1973, Gedam et al. 1974). Also reported are two incompletely identified phenols, perhaps analogous to the cardanol of CNSL, being decarboxylated anacardic acids. One was named semecarpol, and appears to be an undecenylphenol (Pillay & Siddiqui 1931); the other, named anacardol, appears to be a dodecenylphenol (Naidu 1925). There is evidence in the literature that the relative proportions of bhilawanol and anacardic acid vary with the source of the plant material. As well as having vesicant and allergenic properties, the bhilawanols have cytotoxic activity as demonstrated by their effect on 9KB nasal pharyngeal carcinoma cells in culture (Hembree et al. 1978). Anacardic acid has been shown to have anthelmintic activity (against an unidentified species of earthworm) which compared favourably with the activity of piperazine (Chattopadhyaya & Khare 1969). Cross-sensitivity to bhilawanol, ether extracts of marking nut tree leaves and branches, and to an ether extract of the bhilawan nut has been observed in persons with a previous history of poison ivy (Toxicodendron Mill. sp.) dermatitis (Howell 1959). The black tarry sap causes severe dermatitis (Sulit 1940, Flecker 1945, Francis & Southcott 1967). The juice of this plant produces a severe inflammation (Homsey, J.F. - cited by Hou 1978). The oil has been used by the Amboinese as a varnish. The oily fruit has irritant properties (Burkill 1935). This species was described as the most common of the contact poisons of the Philippine Islands; rain dripping off the tree, and the smoke from burning branches produces dermatitis (Burkill 1935). The oil of the pericarp has been used as an escharotic, and the sap produces violent dermatitis (Quisumbing 1951). According to an herbarium note found by von Reis Altschul (1973), "the sap of this tree is very caustic, burning and taking the skin right off". Another note stated that "the bark is macerated and applied to Tinea and eruption of the skin". Both herbarium samples had been collected in the Soloman Islands. The resin of this Javanese plant produces severe dermatitis (Burkill 1935). Backer & Haack (1938) isolated renghol, a 3-pentadecenylcatechol, from the vesicant latex of this plant. This species causes dermatitis in Melanesia (Record 1945). A methanol extract prepared from the fruits of this Sri Lankan species was found to be rich in 3-alk(en)ylcatechols, including penta-, hepta-, and nonadec(en)yl- homologues. Further structural details were not elucidated because "the vesicatory characteristics of the oil … precluded further study" (Carpenter et al. 1980).
The fruits of these two Sri Lankan species have been found to yield phenolic oils with "vesicatory characteristics" (Carpenter et al. 1980). The nature of the phenolic constituents was not reported. The juice can cause dermatitis (Behl et al. 1966). The bark exudate has been found to contain laccol, an incompletely characterised 3-n-heptadecadienylcatechol (Nair et al. 1952b, Puntambekar & Beri 1954). This species was reported to cause dermatitis by Iseki (1932). This species provides Formosan lacquer (Hausen 1970). The juice poisons the skin (Kumada 1940). This is the only species of the genus, and is confined to southern Africa. The latex is irritating, contact with the skin resulting in itching, swelling, a rash, and even blistering (Watt & Breyer-Brandwijk 1962). The sap or latex is irritant in high concentrations, but is also a potent sensitiser (Findlay 1963, Whiting 1971, Heyl 1972, Hindson & Oliver 1975). Urushiols are present in prominent intercellular secretory canals (Ellis 1974). Pruning the plant spatters the sap. It has been alleged that high wind can break the leaves and spray sap droplets on a passer-by who has not even touched the tree. The sap also spreads in a layer on the surface of water, and can produce a sock-like distribution of dermatitis in persons who dangle their feet in contaminated water (Findlay et al. 1974). The sensitising agent appears to be a mixture of 3-n-heptadec(en)ylcatechols, with traces of pentadecyl- and pentadecenyl- catechols (Eggers 1974, Findlay et al. 1974). There are perhaps 12 species in this genus, being natives of Indo-Malaysia, south-eastern Asia, and tropical America. Four species are extensively cultivated throughout the tropics for their edible fruit known as the hog-plum. All parts of the plants have a foetid, turpentine-like odour when broken or bruised; the smell differs in each species and is characteristic (Corner 1952).
Woods & Calnan (1976), referencing data from an unpublished survey of sawmills and woodworking factories in Ibadan, Nigeria, noted that a sawyer who had developed mild papular dermatitis on exposed skin, when patch tested with the sawdust from seven woods he had recently worked with, showed a positive (2+) reaction to sawdust from this species, with weak positive (±) patch test reactions to the sawdust from Pterygota macrocarpus [sic; = Pterygota macrocarpa K. Schum.] (fam. Malvaceae) and from Terminalia ivorensis A.Chev. (fam. Combretaceae). Control tests were not recorded. The tree is cultivated in India for its fleshy fruit which is eaten raw or pickled. The bark of the tree is rubefacient, being used in Indian indigenous medicine for rubbing on the skin over painful joints (Chopra et al. 1958). There are 15 species in south-eastern Asia and western Malaysia. The plants are said to be as poisonous as Melanorrhoea (see Gluta L.) species (Foxworthy 1909), but according to Burgess (1966) the sap is apparently not irritating. Mucocutaneous reactions from this species in the woodworking industry were reported by Hublet et al. (1972). The 15 species of trees and shrubs in this genus are native to eastern Asia and to North and South America. Plants in this genus have formerly been considered to be species of Rhus L., and this nomenclature is still to be found in the literature. Several members of the genus, particularly Toxicodendron radicans Kuntze and Toxicodendron diversilobum Greene are noted for their variability that is due in part to a presumed reversion to an ancestral condition, and in part to a tendency to hybridise with other species of Toxicodendron growing in the vicinity (Gillis 1971). The genus Toxicodendron is the most common cause of contact dermatitis in the USA. The species most commonly encountered is Toxicodendron radicans, the poison ivy, but other species may be more important locally. The sap from crushed leaves of poison ivy and related species, when applied to white paper, will darken on drying. Blackened exudation may also be noticed on bruised plant material. These observations form the basis of the "black spot test" described by Guin (1980a) as an aid to the recognition of these plants. This very rare species has only been found in the state of Sabah in northern Borneo. Gillis (1971) presumes that it contains an urushiol because of his observation that it possesses a resin that darkens with age.
This species occurs on the west coast of N. America, ranging from Baja California to British Columbia. It is less common in the northern areas of its range. Some hybridisation with T. rydbergii Greene occurs in northern areas (Gillis 1971). It is recognised as a cause of contact dermatitis (Legge 1921, Curtis 1960, Gross et al. 1975, Craig et al. 1978). The principal constituents of its urushiol are 3-n-penta- and 3-n-heptadec(en)ylcatechols (Corbett & Billets 1975, Gross et al. 1975). This is quite a rare species occurring in Indonesia and Malaysia. It possesses a toxic effluvium (Gillis 1971).
Several sub-species of poison ivy are recognised, the taxa being distributed in fairly well defined areas. Much of the early research work was carried out on plant material described simply as Toxicodendron radicans, or, more usually, Rhus radicans or Rhus toxicodendron, but at this time many of the sub-species were still considered to be separate species. Listed below are the names of the sub-species together with their previously accepted names and their distribution (Gillis 1971): This taxon occurs in Mexico and Guatemala.
This taxon occurs in Mexico and the south-eastern corner of Arizona, USA.
This is one of the more unusual and rare sub-species which is found in south-western Texas and into Mexico.
Known as Taiwan tsuta-urushi, this sub-species may be found in western and central China and in Taiwan.
This taxon is found in the southern lobe of Ontario, in the Great Lake States, and in the central states and Midwest of the USA.
Known as tsuta-urushi, this taxon occurs in Japan and on the Kurile Islands and Sakhalin region of the (former) USSR. This taxon occurs in southern central USA between the Lower Mississippi Valley and eastern Texas.
This taxon occurs in eastern and south-eastern USA, and in Bermuda and on the Bahama Islands. Specimens have also been found in Nova Scotia.
This sub-species occurs in Texas and Oklahoma, USA. Poison ivy is the most common and widespread species of the Anacardiaceae. It may be found in southern Canada, all of the USA, throughout Mexico, in Bermuda, in the western Bahamas, in Japan, Taiwan, and western and central China, and on the Kurile Islands and in the Sakhalin region of the USSR (Gillis 1971). The early literature refers to the plant as Rhus toxicodendron L. It was introduced into Britain (Nicholson 1899, Nott 1910, Shadbolt 1916) and, according to Anon (1908), was grown in a fairly considerable number of gardens, but instances of trouble rising from it were somewhat rare and scattered. Anon (1908) further noted that most cases seemed to occur in the south-east of England where summers are hottest. Poison ivy is now likely to be found in Britain only in botanic gardens. It has also been introduced into western Europe (Giuseppe 1928, Beurey 1980b), South Africa (Ross 1959), Australia (Aplin 1966), New Zealand, Tasmania (Cleland 1914, Maiden 1914, Nurse 1966, Turner 1972, Apted 1978), Bulgaria (Topalov 1957), Poland (Lukowska 1971), and Russia (Solomatin 1962). However, the plant has not yet developed a reputation as a common noxious weed outside the North American continent, except perhaps in Australia, where it has been planted for the colour of its autumn (fall) foliage and has caused dermatitis in homeowners (Nurse 1966, Apted 1978), and in eastern USSR Dermatitis in the USSR is produced by T. radicans subsp. orientale (Khlebovich 1960, Emeliyanov 1974). Poison ivy as a cause of contact dermatitis has been described on many occasions (McNair 1923, Curtis 1960, Maibach & Epstein 1964, Whiting 1971, Ducombs & Texier 1974, etc.). Even an anecdotal biographical history of poison ivy has been published (Rostenberg 1955). It is estimated that in excess of 50% of the population of the USA is sensitive to poison ivy (Kligman 1958a), this being either a primary sensitivity to T. radicans or a cross-sensitivity to the almost identical sensitisers in other locally common Toxicodendron species. The allergenic material, termed urushiol, is contained within intercellular secretory canals in the stems, leaves, and petioles (Eggers 1974). On exposure to the air, the sap turns black, the reaction requiring oxygen, moisture, and an oxidase (McNair 1923). Blackening of the sap does not render it inert (Kligman 1958a). Heavy contamination of the skin (or fomites) with sap can produce a black lacquer deposit within a few hours (McNair 1923, Mallory et al. 1982). The urushiol is also found on the surface of the leaves and is thus readily accessible. In contact with the eye, it may cause swelling of the eyelid and conjunctivitis. If the cornea is involved, pain, photophobia, and blepharospasm may be experienced (Grant 1974). Brushing past the foliage with unprotected skin may result in a delayed reaction exhibiting a highly typical linear pattern of vesicular dermatitis. One close encounter of this sort is usually sufficient to induce sensitivity. It has been demonstrated that young leaves contain greater quantities of urushiol than do older leaves (Craig et al. 1978, Baer et al. 1980). Direct skin contact with plant material is not a necessary prerequisite. The urushiol, if allowed to contaminate articles of clothing, animals, tools, etc. may subsequently be transferred to human skin. Even burning the plant material may be hazardous if unburnt particles of the plant, or vapourised urushiol is carried away in the smoke. The chemical nature of the urushiol has been well studied. The major constituents are 3-n-pentadec(en)ylcatechols, but small amounts of 3-n-heptadec(en)ylcatechols are also present (Gross et al. 1975, Craig et al. 1978, Baer et al. 1980). There is evidence that the relative proportions of the individual constituents vary with the source of the plant material, but this may be in part the inevitable consequence of incomplete identification of the sub-species being studied. Cross-sensitivity reactions have been demonstrated to many other plants in the genus and family (Keil et al. 1945a, 1945b, 1946, Howell 1959) and to some extent to resorcinol, and to hydroquinone and its monobenzyl ether (Kligman 1958a). Resorcinol sensitive persons are also known to cross-react to hydroquinone (Van der Walle et al. 1982).
This is the most northerly ranging species in the family Anacardiaceae. It ranges from 52° Lat. in the southern provinces of Canada into the northern latitudes of the USA, but also occurring down through the central and southern states of the USA to north-eastern Arizona and western Texas. Hybrids with Toxicodendron diversilobum Greene and with certain sub-species of T. radicans Kuntze may also be observed (Gillis 1971). This species is noted as a cause of delayed contact dermatitis (Gross et al. 1975).
This small tree grows in Central America and in northern South America. The common name manzanillo is applied both to the tree and its timber. The name manzanillo is also applied to the botanically unrelated Hippomane mancinella L. (fam. Euphorbiaceae). Hinchador is the name used in Costa Rica, and means "the sweller". The shrub is of the right height to brush easily against the face and hands (Standley 1927). It has caused severe allergic contact dermatitis with blistering and oedema (Dahlgren & Standley 1944, Standley & Steyermark 1949, Hurtado 1965). In one case (Hurtado 1965), the dermatitis developed two days after sawing the wood and persisted for two weeks. von Reis Altschul (1973) found an herbarium note attributing a case of dermatitis to a specimen of Rhus juglandifolia collected in Guatemala. Sprague (1921) wrote that Humboldt and Bonpland were sceptical as to the alleged ill-effects of remaining under the tree without actual contact taking place: "Lac aquosum, quod arbor stillat, in cute post 2 vel 3 dies ejicit pustulas similes variolis, quamobrem incolae non solum succum sed etiam umbram arboris metuunt, fabulantes eam noxiam esse, praesertim quando post pluvias sol arborem calefecit. Sunt tamen, qui nec post contactum, nec post tritum ullum sentiunt effectum adversum." Triana, on the other hand, was satisfied that the popular idea of the shade of the tree being dangerous was well-founded: "Le Rhus juglandifolia exerce une actione curieuse sur l'homme: l'ombre seulement de l'arbre ou ses émanations, son contact, son approche, la fumée de son bois, produisent, suivant les individus, une irritation avec gonflement accompagné de démangeaisons. L'intensité de ces accidents est presque nulle pour certaines personnes, plus ou moins grave pour l'autres. L'un de nous (Triana) a éprouvé ces effects en récoltant et en desséchant la plante; même action sur une autre personne qui l'avait touchée. Les gens du pays combattent ces affections en faisant des frictions avec de la graisse ou avec de la crème" (Ann. Sc. Nat. sér. 5, xiv. 289;1872). Triana's evidence as to the poisonous nature of Rhus juglandifolia seems to have been overlooked (Kew Bull. 1898, 100). The urushiol of this species has been shown to contain a mixture of 3-pentadec(en)ylcatechols (Nakano et al. 1970). The oleoresin shows haemolytic activity on human red blood cells (Hurtado et al. 1965). Cross reactions have been reported to Toxicodendron radicans Kuntze, Lithraea caustica Hook. & Arn., Mauria puberula Tul., and Toxicodendron vernicifluum F.A.Barkley (Hurtado 1968). Native to China and Japan, this plant is cultivated locally for the fruits from which a wax (sumach wax, Japan tallow, vegetable wax) is extracted for use in varnishes, polishes, ointments, and plasters (Usher 1974). The plant is listed as a popular species for cultivation as a bonsai, a Japanese art form produced by artificially stunting the growth of a tree (Murata 1964). The leaves, fruit, and bark can cause dermatitis (Burry 1969, Guimaraes et al. 1960, Behl et al. 1966. The sap is vesicant (Chopra et al. 1949). The wax has caused dermatitis in workers handling fabrics waterproofed with it (Schwartz et al. 1957). This plant, and not T. radicans, is the commonest cause of "poison ivy dermatitis" in Australia (Czarnecki et al. 1982). The Japanese wax tree was voluntarily withdrawn from sale by several South Australian nurserymen after six or seven workers in one nursery developed dermatitis through handling the plant (Aplin 1976). Majima (1922b) isolated laccol from this species, and identified it as a 3-heptadec(en)ylcatechol.
This species occurs widely in south-eastern USA. Taxonomically, it has been the most misunderstood species of the poison ivy complex. Hybrids with certain sub-species of Toxicodendron radicans Kuntze may be found (Gillis 1971). It is recognised as a cause of delayed contact dermatitis (Gross et al. 1975, Craig et al. 1978).
Lacquer from this tree, known variously as Chinese lacquer, Chinese shellac, Japanese lacquer, or ningpo varnish, was used in China as early as 2255 BC but the art of lacquering was not introduced into Japan until about 250 BC (Toyama 1926). The tree was distributed in Japan before 701 AD. At one time, every farmer in certain parts of Japan was obliged to establish plantations of the tree, and taxes were paid in lacquer (White 1887). The lacquer is obtained by tapping the trees. Incisions are made in the bark, just deep enough to reach the wood. Some lacquer is extracted from felled trees, under water. The latex flowing from the incised trees darkens on exposure to the air. As the quality is highest when the lacquer is light in colour, it is stored in bamboo tubes. A volatile substance is associated with the fresh latex which, because of its poisonous nature, is eliminated from the latex by stirring for several hours in open vessels. The procedures followed in Japan, China, and Burma differ in some particulars (Burkill 1935). Lacquer dermatitis was described in China as early as 453 BC. A good description was given by Ping-yuan-hon-lun (605–609 AD) in China, and later in Wamyo-rui-ju-sho (923–930 AD) in Japan (Toyama 1918), and also by Zan Yun Fang (c. 600 AD) (Toyama 1926). An early European account of lacquer dermatitis was published by Kaempfer (1712). According to Burkill (1935), the risk of dermatitis to tappers is reduced by the fact that they are a special class or caste of highly skilled workmen. Toxicodendron vernicifluum and its lacquer can give rise to dermatitis at all stages from the initial collection of the latex to the final application of the lacquer, and even, it appears, a thousand years later - lacquer from a Chinese jar, which had been buried for about a millenium, caused dermatitis (Toyama 1918). Contact dermatitis from handling the plant itself has been reported by Buraczynski (1903), by Bauer (1940), and by Rost (1914). A girl in North Vietnam developed dermatitis after wearing shoes made of the wood (Holcik 1959). Bullous occupational dermatitis with systemic illness was reported by Antonev et al. (1964). Contact dermatitis from the lacquer has been far more frequently reported because so many such cases have occurred in Western Europe or North America, and because the sources of contact are sometimes exotic and unexpected. Men engaged in hanging embossed Japanese wallpaper are said to have been affected (White 1887). Some individuals become so sensitive that they cannot pass a furniture shop where articles are being varnished without being affected. Others, less sensitive, react only on contact with freshly varnished furniture (Allen 1887). In Hawaiian pineapple factories, cans that were passing through a bath containing one part of lacquer to five parts of gasoline caused dermatitis in those handling the cans (Wayson 1923). A seller of canes used for toy flags developed dermatitis that was attributed to the lacquer on incomplete evidence (Pusey 1923). Lacquered lamp shades have also been incriminated, but inconclusively (Weber 1937). Lacquered bracelets and boxes have caused dermatitis in woodworkers and others (Goldstein 1968). The lacquer on Japanese rifles caused dermatitis in American servicemen sensitive to poison ivy (Toxicodendron radicans Kuntze) (Hinman 1946, Coomber 1947). Contact with a recently varnished bar in Japan caused dermatitis in 12 American officers; it is possible that some were previously sensitised to poison ivy (Etler 1951). In Scotland, subjects sensitive to poison ivy developed dermatitis after contact with varnished boxes (Murrell 1896). For 15 years, a woman had suffered a recurrent dermatitis of the fingers, palms, and wrists; the cause was proved to be lacquered soup bowls (Hollander & Shelton 1937). When used for firewood, the smoke contains highly irritating particles (Holcik 1959). The clinical features are almost infinitely variable, according to the mode and sites of contact, and the degree of sensitivity. A study of affected workers in a factory (Riedel 1940) illustrated some of the problems. Little (1924) noted that those who work with the varnish seem to acquire immunity to its actions. She also recorded that the oil expressed from Thea sasanqua (tea oil; see Camellia sasanqua Thunb., fam. Theaceae) relieves the itching and is used by lacquer workers each evening to remove every trace of the varnish from their hands and arms. Majima (1922a) found the lacquer to contain 3-pentadec(en)ylcatechols, the individual constituents of which were characterised by Sunthankar & Dawson (1954). The urushiol constitutes 35–70% of Chinese lacquer, and a somewhat greater proportion of Japanese lacquer (Toyama 1923, 1926, Toyama & Usuba 1926). Cross-sensitivity to other anacardiaceous plants has been mentioned above. It has been investigated by Howell (1959); the range is wide but variable. Sturua (1963) found sensitivity to T. vernicifluum to be specific with no cross-sensitivity to T. succedaneum or T. radicans; tests were carried out with slices of twigs of the plant.
This species occurs on the North American continent from southern Quebec through the USA to Florida, in the eastern third of the country (Gillis 1971). Stevens & Warren (1907) noted that on wounding the tree, a pale cream-coloured thick poisonous juice exudes in abundance, which begins to darken at once and finally becomes black. T. vernix is recognised as a cause of contact dermatitis (Ducombs & Texier 1974, Gross et al. 1975, Craig et al. 1978). Gross et al. (1975) have shown that the urushiol contains a series of 3-n-pentadec(en)ylcatechols. The clinical features of the dermatoses caused by members of the Anacardiaceae have been described in the individual monographs above. However, the syndromes induced by the more potent sensitisers share certain distinctive features. In previously unsensitised individuals, exposure is followed by a latent period of 9–14 days before dermatitis appears (Biberstein 1929, Field & Sulzberger 1935). In sensitised individuals, symptoms develop from a few hours to several days after contact; Guin (1980b) reports that he observed reactions as early as 4 days and as late as 15 days after identical applications of the sap of Toxicodendron radicans subsp. negundo to various parts of his own forearm. Inadvertent application of the sap from T. radicans subsp. divaricatum on a pair of contaminated sunglasses to parts of the face elicited a reaction within 5.5 hours. The first symptom is intense pruritus; papules soon appear, often in a linear pattern in the case of poison ivy contact, and these evolve into vesicles or bullae. Any and all parts of the body may be affected in severe cases, the allergenic material being easily carried by the fingers to sites remote from the points of initial contact. The allergenic material is not, however, present in the vesicle fluid. Areas of thicker skin are less susceptible. Except in regions well protected by hair, oedema may be considerable, and particularly so on the eyelids and male genitalia. The evolution of the eruption occurs in crops, affecting firstly the sites where most allergen has been absorbed, and then successively the less heavily contaminated sites or sites of thicker skin. The dermatitis has commonly reached its full extent after 48 hours. Healing occurs within 2–3 weeks unless there is re-exposure to the offending allergen. Scarring does not occur unless secondary infection has been introduced. Hyperpigmentation is a common complication of poison ivy dermatitis in black skin, uncommon in Caucasian skin (Fisher 1977, Taub 1965); hypopigmentation can also occur (Kligman 1958a). Perianal dermatitis from eating poison ivy leaves was described by Dakin (1829). If plant material is ingested, there may be vomiting, diarrhoea, and neurological symptoms simulating atropine poisoning - drowsiness or stupor, convulsions, delerium, fever, and pupillary dilatation. Sensitive patients challenged with an extract of poison ivy orally developed degranulation of circulating basophils within an hour (Shelley & Resnik 1965). Nephritis too may complicate poisoning, either following ingestion or after massive cutaneous vesiculation (Templeton et al. 1947, Rytand 1948). Acute or chronic glomerulonephritis has occurred during Toxicodendron dermatitis (Devich et al. 1975, Schaffer et al. 1951, Rytand et al. 1948); glomerular deposits of complement and the presence of circulating immune complexes suggested a type III hypersensitivity mechanism. One case of erythema multiforme associated with poison ivy contact dermatitis has been reported by Schwartz & Downham (1981). This complication was not associated with any systemic symptoms, and the possibility of it arising from the treatment of the dermatitis with antihistamine was considered. Contact sensitivity to Toxicodendron is most commonly acquired in childhood or early adult life, and tends to decline in later life. Ninety percent of those exposed become sensitised, and such exposure is the commonest cause of contact dermatitis in the USA. There is no evidence for familial predisposition to acquiring sensitivity, but atopic individuals may be less susceptible (Jones et al. 1973). It has been estimated that perhaps 50% of the population of the USA has acquired sensitivity to poison ivy and other urushiols (Kligman 1958a), and only 10–15% of the population is truly immune (Epstein 1973). There is no evidence that children are any more or less susceptible than adults; incidence of sensitivity in all the younger age groups is a measure of exposure to the allergenic material (Straus 1931, Epstein 1961). Immunity in Asiatics has been ascribed to exposure to Mangifera in early life (Epstein & Claiborne 1957). Various methods of hyposensitisation have been advocated, including the application of gradually increasing doses to the skin (Maisel 1932), and graduated dosage orally of 10% cashew nut oil (Kligman 1958b). A patient's attempts to desensitise himself by chewing poison ivy leaves caused stomatitis, and dermatitis of the face and perianal skin (Silvers 1941). Oral hyposensitisation was demonstrated in some individuals (Kligman 1958b) and confirmed in a study of larger groups (Epstein et al. 1974). An adequate quantity of purified urushiol must be administered during a sufficiently long period of time, and observation is required for cutaneous and systemic complications (Shelmire 1941, Schaffer et al. 1951). Experiments in guinea pigs (Baer et al. 1966) showed that the capacity of the urushiols to induce delayed contact sensitivity depends on the nature of the ring substituents. Catechol and 3-n-alkylcatechols were equally effective in inducing sensitivity, but the degree of sensitivity as well as cross-reactivity depended upon the length of the alkyl chain. Dermal toxicity was unrelated to sensitising capacity (Baer et al. 1967). Further studies (Baer et al. 1968) emphasised the importance of the alkyl chain in determining antigenic specificity and non-reciprocal cross-reactivity. Cross-reactivity within the Anacardiaceae was studied in guinea pigs by Oliveira Lima (1953) who used the oleoresin from Lithraea molleoides Engl. as the primary sensitiser. The guinea pigs were tested with the oleoresins of 12 species from 7 genera. Only Lithraea brasiliensis Marchand, Lithraea caustica Hook. & Arn., and Toxicodendron radicans Kuntze gave definite cross-reactions. In a clinical study involving both open and closed patch tests in patients primarily sensitised to poison ivy (Howell 1959), all patients showed cross-sensitivity to poison oak, whilst cross-sensitivity to other genera occurred frequently in open patch tests, and very frequently in closed patch tests. Cross-sensitivity within this family must be considered to be general unless it has been positively excluded. Cross-sensitivity to Ginkgo biloba L. (fam. Ginkgoaceae) and to various members of the family Proteaceae should also be considered to be distinctly possible. More obscure sources of cross-sensitivity might be found among certain phenolic materials used medicinally, including resorcinol, hexylresorcinol, Castellani's Paint, etc. (compare Kligman 1958, Caron & Calnan 1962, Keil 1962, Cronin 1973a, Marks & West 1978, Waddell & Finn 1981, Burrows & Irvine 1982), wheat bran (Wenkert et al. 1964), and also certain alkyl quinones (Hausen 1981). The following suggestions for treatment of poison ivy and other urushiol-elicited dermatoses are adapted from Mitchell (1982). The aim of the treatment is to make the patient comfortable whilst the dermatitis resolves: Mild to moderate dermatitis 1. Provide continuous cold, wet compresses of tap water or Burow's solution 1:40. A modified Burow's solution may be prepared conveniently by dissolving one Domeboro(TM) Tablet in 1 quart (a little over 1 litre) of water. When the eruption is widespread, three 10 minute cool baths daily have a soothing effect. 2. As the vesiculation subsides, change to topical applications of calamine lotion mixed in equal parts with water. 3. As the skin begins to dry, change to topical application of a corticosteroid cream. Such creams, however, have little more that a placebo effect in poison ivy and similar dermatoses. The simpler the topical therapy is kept, the better. Avoid calamine lotions with additives, topical antihistamines, and "-caine" compounds, otherwise surprisingly violent exacerbations may ensue. Relief of pruritus by oral medication is notoriously difficult and varies in efficacy from one patient to another. Aspirin in divided doses to a total of 3000 mg per 24 hours is often helpful and is probably not prescribed often enough for the relief of itching. The antipruritic effect of antihistamines appears to be in proportion to their sedative effects. There are many types of antihistamines to choose from - the oral administration of diphenhydramine hydrochloride 50 mg at night and in addition chlorpheniramine maleate 8–12 mg three times daily is recommended. It is important to warn the patient of the sedative effect of this treatment, particularly in respect to driving a motor vehicle, working with moving machinery, etc. If antihistamines are taken, alcohol should not be taken. Localised oedema, which may result from involvement of the face, neck, and anogenital area, may indicate a need for oral corticosteroid therapy [see below]. Severe dermatitis The patient suffers agonising discomfort. He should rest at home in loose-fitting clothing and avoid overheating, caffeine, and alcohol. Compresses or bathing, as noted above, should be used for 10 minutes every 2–3 hours. A dose of 40 mg prednisolone daily, in divided doses, is prescribed, to be taken with milk between small, frequent meals. This is adequate treatment for some cases. For severe cases, experienced dermatologists have recommended an even larger dose of corticosteroid (80 mg of prednisolone) in the first 24 hours. In order to obtain response in 98% of patients, a daily dose of 80–100 mg is required. The dose is gradually reduced during 7–10 days. Flare-ups are frequent if withdrawal is too rapid, or if alternate day dosage is used. It is better to taper the dose during 20 days. Such short courses of corticosteroid therapy carry the usual risks, but the risks of such short-term therapy in otherwise healthy individuals are negligible compared with the risks of prolonged corticosteroid therapy for skin diseases. In the treatment of acute dermatitis with systemic corticosteroids, one should be concerned principally about the patient who may have peptic ulceration. A significant complication is central nervous stimulation - the patient cannot sleep. No-one should administer poison ivy or similar such extracts in the management of the acute disease. This is ill-advised and immunologically unsound. Such administration may produce no effect, or the dermatitis may be aggravated. The symptoms of severe ocular involvement may be relieved by topical use of atropine and corticosteroids (Grant 1974). Complications The patient is usually better off at home. Pyoderma secondary to the dermatitis, and principally consisting of boils, may be managed by standard methods including appropriate systemic antibiotic therapy with culture organism sensitivity control. Prophylaxis Many methods have been devised to destroy the offending plants (Chesnut 1896, Byram 1931, Crooks & Klingman 1968, Maibach & Epstein 1964, Gillis 1975) or to otherwise protect the patient, but none is wholly effective (Howell 1943, Birmingham 1969). Recurrence or prolongation of the dermatitis is caused by re-exposure to urushiol or possibly to some other immunochemically related material. Instruct the patient to have potentially contaminated clothing, including shoes, towels, sheets, sleeping bags, and other items washed or cleaned. A pet dog should also be washed several times. The allergenic oleoresins of poison ivy and related plants are non-volatile oils which oxidise very slowly, if at all, in the absence of moisture. Children, animals, rocks, vegetation, tools, athletic or hiking equipment, furniture, automobiles and their accessories, etc., may transfer allergen to sensitive persons. Instruction on the nature and botanical distribution of poison ivy and other relevant members of the families Anacardiaceae, Ginkgoaceae, and Proteaceae is a vital prophylactic measure. A physician would, therefore, benefit by possessing a book or reprint of a paper with coloured pictures of locally suspect species to show to patients (two examples of useful papers: Guin & Beaman 1980, Guin et al. 1981). Avoidance of exposure may, nevertheless, prove to be impossible. Barrier creams, topical detoxicants, and the like give inadequate protection. Thorough washing after exposure does not prevent a severe dermatitis in highly sensitive persons; it may, however, reduce the reaction in those who are less sensitive. Harsh soaps and vigorous scrubbing offer no advantage over simple soaking in cool water. The popular "herbal" remedy for the prevention of poison ivy dermatitis in the USA involves application of the sap of the jewelweed (Impatiens biflora Walt., fam. Balsaminaceae). This has been shown to be no more effective than water alone in preventing dermatitis (Guin & Reynolds 1980). Immunological prophylaxis is sometimes possible. It is however a rigorous procedure demanding supervision by a physician since the danger of untoward effects is considerable. Large quantities of active allergens must be ingested over long periods of time, and, when therapy is stopped, sensitivity rapidly returns. This form of treatment should be reserved for very sensitive persons who, for reasons of work or environment, cannot avoid exposure to the allergens. Of the experimentally proven agents (crude poison ivy oleoresin, synthetic pentadecylcatechol, and cashew nut shell oil), only the crude poison ivy oleoresin is available at this time. Many companies supply it in over-the-counter preparations, but these are either wholly inactive or are so dilute as to be valueless for prophylaxis. A reliably active oleoresin is supplied by Hollister-Stier Laboratories (107 South Division Street, Spokane, Washington 99202). The standard desensitisation kit contains 15 ml each of 1:100, 1:50, and 1:25 dilutions of oleoresin in corn oil (a total of 1050 mg of allergen). Instruction sheets are enclosed in the package. The important point is to increase the dose of the allergen in a dropwise fashion as rapidly as the patient's tolerance allows. Onset of itching means that the increment is too great. When this happens, reduce the dose by 2–5 drops; after pruritus subsides, increase it again. Other untoward reactions such as dermatitis, urticaria, or pompholyx may occur if the cardinal symptom of pruritus is ignored or is not recognised. Little is known about the systemic toxicity potential of such regimens. The preparation may occasionally cause pruritus ani; dividing the dose tends to reduce this complication. The total dose for hyposensitisation varies between 2000 and 3000 mg. After the first set is completed, 1:25 dilutions should be used in doses of 1–1.5 ml daily. Adequate hyposensitisation is determined by patch test responses (experimental) and clinical observation (practical). The procedure may be started in late winter and continued as a maintenance dose until July. Clinically, patients have some protection until September or October, when the opportunity for exposure usually dwindles. Sensitivity requires about 6 months to return to pre-treatment levels. Some persons must remain on therapy all the year round. In general, "treatment is worse than the disease", and thoughtful, educated avoidance of exposure to the offending material is the mainstay of prophylaxis. The possibility of an improved method of prophylaxis being developed has arisen following publication by Watson et al. (1981) of some immunologic studies on guinea pigs. It was found that the development of contact sensitivity to poison ivy urushiol was inhibited by intravenous injection of the diacetate esters of poison ivy and poison oak urushiols two weeks prior to attempted sensitisation. By a similar technique, sensitised guinea pigs were rendered hyposensitised by injection of urushiol diacetates. Concomitant hyposensitisation to poison sumac urushiol and cashew nut shell liquid was also observed. References
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