Picture of Cercarial Dermatitis (Swimmer's Itch)

Cercarial dermatitis goes by several names – also known as swimmer's itch, is an itchy rash caused by a very small parasitic worm. It is contracted by swimming or wading in infested freshwater lakes or ponds. The parasite is excreted from water fowl or rodents, enters a snail, and eventually leaves the snail and comes into contact with human skin. The rash begins to itch while in the water, but after a few hours disappears. However, in 10-15 hours the itch and rash re-appears as tiny red bumps that can turn into blisters. The rash usually goes away in a week if not treated.