Photosensitivity and allergy to aromatic lichen acids, Compositae oleoresins and other plant substances

Abstract

Patients [16] with verified light sensitivity to both UVB and UVA wavebands showed allergic reactions to various lichen plants (Parmelia spp., Hypogymnia spp., Pseuodovernia spp., Cladonia spp., Platismatia spp., Physcia spp., Umbilicaria spp. and Cetraria spp.). Among the aromatic lichen compounds, atranorin was observed to be the most frequently involved allergen but also several other isolated lichen acids were immunologically active: d-usnic, evernic, stictic, fumarprotocetraric, lobaric, salazinic, diffractaic and physodic/physodalic acid. Several patients showed allergy to other plant substances from other sources such as 7 different species from the Compositae family [Anthemis cotula, Ambrosia artemisiifolia, Helenium autumnale, Centaurea cyaneus, Chrysanthemum spp., Tanacetum vulgaris and Achilla sp.], alantolactone, balsam of Peru, colophony and wood tars. Sensitivity to known photosensitizers was observed in 4 patients. Aromatic lichen acids are UV-absoring substances and several are evidently able to photosensitize human skin.