Swimmer's itch is caused by a blood fluke common in waterfowl. The itching is caused
when the fluke, while in the immature stage of its life cycle, mistakes you for
its primary host -- waterfowl -- and burrows into your skin. Aside from the annoying
itching, swimmer's itch is harmless to humans. The irritation can last from
two days to several weeks, depending on the individual's susceptibility. Preventive
measures can be taken, and there are no permanent effects from swimmer's itch.
Our web page on Swimmers Itch.