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Myroxylon - Ononis

(Pea or Bean family)


Myroxylon L.f.

In their revision of the genus Myroxylon, Bagnatori Sartori et al. (2015) recognised two species, Myroxylon balsamum Harms and Myroxylon peruiferum L.f. Whilst acknowledging that previous treatments recognised infraspecific taxa of Myroxylon balsamum based mostly on differing chemistry of the balsams that exude from the damaged trees, these authors did not consider these traits to be consistent and thus did not recognise infraspecific taxa in their treatment. These trees occur from Central America to tropical South America.

Myroxylon balsamum Harms
[syns Myrospermum pereirae Royle, Myroxylon balsamum Harms var. balsamum, Myroxylon balsamum Harms var. pereirae Harms, Myroxylon pereirae Klotzsch, Myroxylon toluifera Kunth, Toluifera balsamum L., Toluifera pereirae Baill.]

This tree is the source of balsam of Peru (Balsamum Peruvianum) and of balsam of Tolu (Balsamum Tolutanum). To obtain balsam of Peru, the trees are beaten, then scorched with a torch to cause part of the bark to separate from the trunk. Within a few days, the bark drops and the balsam exudes from the exposed wood. This is soaked off with rags and boiled in water (Trease & Evans 1966).

Contact sensitivity to wood of the tree was observed by De Carvalho (1956).

Contact dermatitis from balsam of Peru was recognised in Germany in 1880 and France in 1889 (Cummer 1927, Touton 1932). Early authors described systemic toxicity from absorption of the balsam which had been applied for treatment of scabies and to the nipples of a nursing mother (Cummer 1927).

Balsam of Peru is a mixture of many different substances and as a rule sensitisation leads to a complicated pattern of multiple allergies which vary from one patient to another (Hjorth 1959). Balsam of Peru contains a number of simple chemicals (cinnamic acid, benzyl cinnamate, vanillin, benzyl benzoate and benzoic acid) which constitute 60 percent of the total while the remaining 40 percent consists of resins. Patch tests with the low molecular weight ingredients yield inconstant positive reactions and half of the patients studied by Hjorth (1959) showed negative reactions to all:

Results of patch tests with low molecular weight ingredients of balsam of Peru (103 cases) (from Hjorth 1959).

Ingredient / Positive reactions

Cinnamic acid / 27 cases
Benzyl cinnamate / 19 cases
Vanillin / 15 cases
Benzyl benzoate / 12 cases
Benzoic acid / 10 cases
One or more positive / 54 cases
All negative / 49 cases

He therefore concluded that the important allergens must be found in the resinous fractions. The exact composition of these resins is unknown but they are thought to be polymers of esters of coniferyl alcohol with benzoic acid and cinnamic acid. In his series 70 patients (85 percent) showed positive patch tests to coniferyl benzoate and sometimes the patch test was followed by a clinical aggravation (a focal flare) and sensitisation induced by patch testing was observed in nine of 27 patients. These observations supported the assumption that this substance is one of the most important allergens in balsam of Peru. By dry heat, coniferyl benzoate is decomposed, among other compounds to isoeugenol and eugenol. Hjorth (1959) found that isoeugenol gave positive reactions in 83 of 132 patients examined (63 percent). Vanillin is also related to coniferyl benzoate, and although reactions to pure vanillin are uncommon 34 of 63 patients showed positive patch tests to natural vanilla (Bourbon). Cross-sensitisation is also seen between balsam of Peru and cinnamon (Cinnamomum), benzoin storax (Styrax), and orange peel (Citrus). In the last named instance, the resinous fraction of orange peel is possibly responsible since limonene, linalool and the coloring matter do not appear to be causative.

Hjorth (1961) provided a comprehensive monograph on eczematous allergy to balsam of Peru. The presently known cross-reactions are tabulated (Table). The constituents of balsam of Tolu were investigated by Wahlberg et al. (1971).

24% of 101 children who had dermatitis and 6% of 284 adults who had dermatitis showed positive patch test reactions to balsam of Peru (Fregert and Moller 1963).

14/64 patients with leg ulcers showed positive patch test reactions to balsam of Peru (Van Dijk et al. 1973). 64 (18 males and 46 females) of 712 individuals showed positive patch test reactions to balsam of Peru. In 18 of 64, contact sensitivity to the balsam was considered to be the main cause or a contributory cause of hand eczema (Agrup 1969).

Cross-reactions and sources of allergic contact dermatitis from balsam of Peru and cross-reacting materials (Collins and Mitchell 1975).

Cross-reactions to

Plant Materials:

Cinnamomum — cinnamon
Eugenia — clove
Citrus — orange peel
Liquidambar spp. — storax
Styrax spp. — benzoin
Pinus spp. — rosin
Vanilla planifolia — vanilla
Myroxylon pereirae — balsam of Peru
Myroxylon balsamum — balsam of Tolu 


Cinnamic aldehyde
Cinnamic acid
Cinnamic alcohol
Benzoic acid
Benzyl benzoate
Benzyl alcohol

Sources of Exposure:

Therapeutic and over-the-counter applications, suppositories, liquids in dentistry, essential oils, cosmetics, hair tonics and lotions, perfumes, flavours, cough mixtures, throat lozenges, balsams of pine and spruce (Pinaceae), pastries and cakes with essences, Danish pastries, caramels, cola-type drinks (Cola), toothpaste, some wines and liqueurs (Vermouth, Curacao), poplar buds (Populus) for bee-keepers.

Fisher (1974) discussed the clinical significance of positive patch test reactions to balsam of Peru, referring to perfume dermatitis, occupational dermatitis in dentists, bakers, bee-keepers, painters, violinists and laboratory technicians, to dermatitis from topical medications and sunscreens, flavoring agents, orange and vanilla and cross-sensitivity with resorcinol monobenzoate used in certain cellulose ester plastics (steering wheel, sunglasses, hearing aids and ball-point pens).

Although balsam of Peru has been less used in medications in recent years in Europe, contact sensitivity to the balsam and to wood tars (Pinaceae) has increased suggesting that other sources of sensitisation (perfumes in toilet soaps and cosmetics) are relevant (Ølholm-Larsen and Heydenreich 1976).

Cinnamic alcohol produced positive patch test reactions in 13/60 perfumery workers who had dermatitis (Gutman and Somov 1968). The other positive reactions were to kumarin (= coumarin) (4/60), citronellol (2/60), orange oil (3/60), hydroxycitronellal (2/60), clary sage oil (2/60), vanillin (2/60), acetylanizol (2/60), lemon oil (1/60), phenylethylalcohol (1/60).

Of 36 patients contact sensitive to balsam of Peru 22 (61%) showed positive reactions to wood tars (Ebner 1974).

Individuals contact sensitive to balsam of Peru can also be contact sensitive to resorcinol monobenzoate (Calnan 1975a).

Active sensitisation by patch testing with balsam of Peru was recorded by Calnan (1975b).

In some balsams and essential oils are found benzyl alcohol, benzyl benzoate, benzyl cinnamate and benzyl salicylate. The adverse skin effects of these compounds were reviewed by Opdyke (1973).

Immediate reactions to balsam of Peru were cited by Rudzki and Grzywa (1976) and by Friis and Hjorth (1973).

4.8% of patients with leg ulcers were contact sensitive to balsam of Peru (Angelini et al. 1975).

Neorautanenia mitis Verdc.
[syns Dolichos mitis A.Rich., Dolichos pseudopachyrhizus Harms, Neorautanenia pseudopachyrrhiza Milne-Redh., Pachyrhizus orbicularisWelw. ex Baker, etc.]

The root / tuber of this plant is recorded as being toxic to insects and fish. Referring to Neorautanenia pseudopachyrrhiza, Dalziel (1937) and Watt & Breyer-Brandwijk (1962) noted that in Nyasaland, the flesh of the tuber of a plant, which is probably this species, produces an eczematous eruption if rubbed over the body.

[Further information available but not yet included in database]


120 species are found in regions from Europe and the Mediterranean to central Asia. O. viciaefolia (syn. O. sativa) known as holy clover is grown for forage.

Onobrychis sativa

Dermatitis from this species was reported by Matras (1931).

Ononis L.

This is a genus of about 75 species of shrubs and herbs found in Europe, the Canary Islands, Mediterranean regions, Ethiopia and Iran. Several of the species bear thorny lateral branches (Mabberley 2008), the best known being Ononis spinosa L. This and a few other species may occasionally be found in cultivation as ornamentals (Hunt 1968/70).

Ononis spinosa L.
[syn. Ononis campestris Koch & Ziz]
Prickly Restharrow, Spiny Restharrow, Cammock

According to Wren (1975), a preparation of the root of this spiny plant has been used in traditional medicine as a wash for ulcers. Usher (1974), on the other hand, notes that a decoction of the stem and leaves has been used to treat skin diseases.

Richard J. Schmidt

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