Sunflower allergy. On the constituents of the trichomes of Helianthus annuus L. (Compositae).

Sesquiterpene lactones (STL) of the sunflower, occurring in fragile multicellular capitate glandular hairs, have been shown to display a remarkable sensitizing capacity when investigated by experimental sensitization in guinea pigs. The strongest response was induced by the hemiketal form of 1-O-methyl-4,5-dihydroniveusin A. The STL content of 50 capitate glands was sufficient to elicit a remarkable response in the guinea pigs. Thus, touching a sunflower plant (with up to 1000 capitate glands per cm2) may lead to the release of sufficient STL to sensitize humans, and these substances can be considered to be responsible for the cases of allergic contact dermatitis described in sunflower growers since 1906.