Schistosomiasis, cercarial dermatitis, and marine dermatitis.

The three anthropophilic species of schistosomes produce local or systemic reactions that are a reflection of host interaction with the stage of the parasite. Dermatitis schistosomica is a transient, local irritant or hypersensitivity reaction during the penetration phase of the cercariae. Early nonspecific reactions are characterized by a severe, transient, systemic, immune-complex disease referred to as Katayama disease, which occurs during migration of the juvenile worm in the bloodstream. Late nonspecific reactions are characterized by a mild, transient hypersensitivity reaction during oviposition by adult worms. Specific late cutaneous manifestations are rare and are produced by the ectopic migration of ova or worms into the skin, with asymptomatic or symptomatic, chronic, granulomatous, and fibrotic mucocutaneous lesions with variable morphologic characteristics. The avian schistosomes produce a cercarial dermatitis that is a more severe form of dermatitis schistosomica but lacks systemic complications and reflects the host reaction to the destruction of the cercariae in the skin. Marine dermatitis or "sea bather's eruption" is probably an irritant or toxic transient reaction of unknown origin with no systemic implication, whereas "Dogger Bank itch" is an allergic contact eczematous dermatitis caused by a metabolite produced by a marine organism.