Chimaphilin is a yellow naphthoquinone which occurs naturally in various chimaphila and Pyrola species. In Chimaphila umbellata (winter green) and C. maculata, it is a major constituent. Folk medicine recommends the leaves of Chimaphila species as a topical application to treat skin diseases. Since 1887, winter green is claimed to have caused dermatitis and to have been responsible for "idiosyncrasy". Experimental sensitization using the open epicutaneous as well as Freund's complete adjuvant technique has now revealed that chimaphilin is a moderate contact sensitizer.