Swimmer's Itch

(cercarial dermatitis, shistosome dermatitis)

Swimmer's itch is a skin rash caused by a parasite (shistosomes) that ordinarily infects birds, semi-aquatic mammals, and snails. Common grackles, red-winged blackbirds, ducks, geese, swans, muskrats, and moles have been found to carry the parasite. As part of their developmental life-cycle, these parasites are released from infected snails, migrate through the water, and are capable of penetrating human skin. After penetration, these parasites remain in the skin and die, but can cause an allergic reaction in some people. The parasite does not mature, reproduce, or cause any permanent infection in humans.

Swimmer's itch fact sheet (PDF,  24 KB)Hmong (PDF,  26 KB)Spanish (PDF,  21 KB)

Last Revised: January 30, 2015