Lichen extracts.
Lichen-derived additives to commercial products are becoming a more frequent cause of allergic contact dermatitis. The most common lichen-derived additives are usnic acid and oak moss absolute. Both are useful for screening patients using "natural" or "botanical" products that may contain lichen-derived additives.
Schalock
Peter C
PC
Department of Dermatology, Massachusetts General Hospital, Harvard School of Medicine, Boston, MA, USA.