Lichen picker's dermatitis (Cladonia alpestris (L.) Rab.).

The frequency and immunological background of dermatitis occurring in lichen pickers during the 3- to 4-month picking season were studied in a small community in northern Finland. Thirty of 164 lichen pickers had suffered from dermatitis at least on the fingers and the dorsa of their hands, and many of them also had dermatitis on their forearms, faces, etc. Fifteen of them were subjected to epicutaneous and photo-epicutaneous testing with crushed Cladonia alpestris (L.) Rab. and some fractions of it. Allergic contact reactions were seen in nine subjects, three of whom also had positive photo-epicutaneous test reactions from lichen allergens. No immediate reactions were seen in scratch or scratch chamber tests with crushed Cl. alpestris or with its alcoholic extract.