Bather's itch, also called schistosome DERMATITIS and common in many tropical and subtropical parts of the world, is the term given to a blotchy rash on the skin occurring in those bathing in water which is infested with the larvae of certain trematode worms known as schistosomes (see SCHISTOSOMIASIS). The worm is parasitic in snails. The skin rash is caused by penetration of the skin by the free-swimming larval cercaria.