Plant taxonomists have undertaken a major revision of the Liliaceae, reducing it from a family of nearly 5000 species to one comprising 350 species in 10 genera. These are bulbous plants found in the northern hemisphere, being particularly numerous from south-west Asia to China. The ejected species have been segregated into a number of smaller families, many of which are liable to further taxonomic re-organisation because of the anomalies so generated (Mabberley 1997).
Representatives from all 10 genera may be found in cultivation as ornamentals. Lilies (Lilium L. spp.) and tulips (Tulipa L. spp.) are of especial commercial importance because of their outstanding horticultural merit.
Tuliposide A, from which the allergenic tulipalin A (= α-methylene-γ-butyrolactone) is released has been detected in Erythronium L. spp., Tulipa L. spp., and Gagea L. spp.
Nadkarni (1976) records that in Indian traditional medicine, the leaves of this plant are applied to wounds and bruises.
Of some 25 species in this genus, one, Erythronium dens-canis (dog tooth violet) is distributed through Europe, temperate Asia and Japan; the remaining species occur in North America. Many species are cultivated. E. dens-canis is frequent in gardens in Western Europe.
Some species have been shown to contain α-methylene-γ-butyrolactone, which is an allergen in Tulipa. This allergen may also be present in species not yet investigated.
Only a few workers in specialist nurseries are likely to come sufficiently frequently into contact with Erythronium for these plants to be primary sensitisers. However they may well induce reactions in those already sensitised to the ubiquitous tulip.
According to (1975) the fresh leaves are used as a poultice in scrofulous ulcers [= scrofuloderma?] and tumours, together with an infusion taken internally in wineglassful doses. It is interesting to note that Wren (1975) uses exactly the same form of words to describe the use of the botanically unrelated Ophioglossum vulgatum L. (fam. Ophioglossaceae) — the English Adder's Tongue.
This north temperate genus contains over 80 species, many of which are cultivated. Two of the most popular, Fritillaria meleagris L. (snake's head) and Fritillaria imperialis L. (crown imperial) are said to be irritant (Pammel 1911).
Very many of the 80 species of this north temperate genus are stately and beautiful plants and are widely cultivated, yet fully authenticated accounts of undesirable effects on the skin are rare. Lilium longiflorum and Lilium superbum L. (Turk's cap lily) have been listed as irritant (Weber 1937).
There are about 100 species, widely distributed through Europe, West and Central Asia and North Africa. However tulips are cultivated in most countries in which the climate is suitable. The original development of garden tulips took place in Turkey, whence they were introduced to Western Europe in the 16th century. Their subsequent development has been largely the work of Dutch horticulturalists, who by selection and hybridisation have produced an immense range of types and cultivars. The natural species from which modern garden tulips were derived are still a matter for speculation. Although the hybrid garden tulips account for the great bulk of the tulip bulb trade, many of the species have a more refined beauty and are often cultivated.
Those most exposed to the risk of dermatitis from tulip bulbs are the collectors, sorters and packers in the large bulb nurseries of Holland and Cambridgeshire and Lincolnshire in England. The incidence of dermatitis is high, although few of those affected may seek medical advice, for what is regarded as a known hazard of the occupation. In one nursery 8 of 12 employees were affected (Klaschka et al. 1964). Florists and flower arrangers as well as nurseries may have frequent contact with the cut flowers.
By using paper chromatography to isolate ethanol-soluble fractions and then patch-testing with the chromatograms, Verspyck Mijnssen (1967) was able to detect an allergenic principle, but it could not be obtained in crystalline form. Brongersma-Oosterhoff (1967) isolated the compound and identified it as α-methylene-γ-butyrolactone. In the plant this is bound as a glycoside. It is probable that in this glycoside-enzyme-glucose + lactone system, only the lactone is allergenic. The same substance was independently isolated by Bergman et al. (1967) in a study of a fungicidal substance formed during the early stages of bulb development. Other antibiotic lactones have been isolated (Tschesche et al. 1968), but there is evidence of only one allergen in tulips (Verspyck Mijnssen 1969).
The concentration of allergen is highest in the bulb, less in stem and leaves, and least in the petals. The main site of the allergen in the bulb is the epidermis of the scales. The content of the allergen diminishes rapidly in the outermost scales during the last weeks of growth, immediately before harvest. During this period the outermost scale forms the leathery brown skin, which is not allergenic. In the second and deeper layer of scale, which remains white and fleshy, the allergen persists during storage (Bergman 1968).
Experienced florists have often found that some cultivars cause dermatitis more frequently than others, e.g. 'Preludium' and 'Rose Copeland' (Van Der Werff 1959). Bertwistle (1935) also found the latter cultivar to be more irritant than others. Some florists who have become sensitised to tulips find that they can handle some cultivars but not others (Rook 1961). Bulb patch tests with nine cultivars (Klaschka et al. 1964) showed no differences between the reactions. Patch-testing supplemented by gas chromatography (Verspyck Mijnssen 1969) showed tkat only one cultivar ('Red Emperor' = 'Madame Lefeber') contained less bulb allergen than the other eleven studied. However not only quantitative factors are involved in the causation of plant dermatitis; structural variations may well influence the release of the allergen from damaged plant tissues; it would be premature to dismiss practical observations which may solve employment problems.
Three main clinical syndromes are recorded. The first is an irritant reaction affecting bulb handlers. Investigations in Britain (Bertwistle 1935) indicated that up to 85% of workers were affected by tingling and tenderness of the finger-tips about 12 hours after slicing the bulbs. Granulation tissue formed beneath the nail, followed by onycholysis, transverse splitting of the nail plate, and in severe cases by subungual abscesses (see also Overton 1926). This irritant effect is a component of the classical syndrome known as "tulip fingers". Patch tests with pure tulip allergen 1: 600 gave positive reactions in all control subjects. However all patients with tulip fingers gave positive reactions also to a test with a one in 20,000 dilution of the allergen, to which controls did not react (Hjorth and Wilkinson 1968). In tulip fingers the changes described above are combined with those attributable to the allergic reaction: erythema and scaling, later complicated by hyperkeratosis and fissuring, develop in a pattern determined by the precise manner in which the individuals occupation requires him to handle the bulb.
Other patients develop a more extensive eczematous dermatitis on the hands, with some dissemination to arms, face and genitalia. These more extensive patterns occur in some bulb handlers (Verspyck Mijnssen 1968, Rappaport and Walker 1936, Caulfield 1936) but are seen particularly in those who handle the cut flowers. Further reports on the observed manifestations are provided by Baefverstidt 1936, Touraine and Neret 1938, Flandin and Ukrainczyk 1938, Osborne and Putnam 1932, and Gore 1962.
The dust in tulip sheds may precipate conjunctivitis, rhinitis and asthma and reaginic responses to tulip antigens can occur (Van der Werff 1959).
As the pure tulip allergen is not readily available, patch tests may be performed with outermost bulb scales, after removal of the brown skin. To obviate dependence on seasonal supplies extracts may be prepared from bulbs which have been tested for allergenicity. The cultivar 'Apeldoorn' is recommended (Hjorth and Wilkinson 1968). The following extracts are suitable:
i. A 96% ethanol extract of tulip bulbs, which is stable for some months in a refrigerator; or preferably
ii. an extract prepared by shaking fresh bulbs for 90 minutes in 80% acetone in water. 1% of this extract in 70% ethanol is used for patch testing.
Severely affected workers may have to change their occupation as piece workers seldom find it satisfactory to work in gloves. It should be remembered that the tulip allergen is present also in Alstromeria, and Erythronium.
Sensitivity to tulip has also been reported in a garlic-sensitive patient by Bleumink and Nater (1973).