swimmer's itch

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An itching inflammation of the skin caused by parasitic larval forms of certain schistosomes that penetrate into the skin, occurring after bathing in infested fresh or salt water.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a sensitization reaction to repeated invasion of the skin by cercariae of schistosomes