Swimmer's itch is an allergic reaction to a parasite. Infected birds and mammals pass the eggs in feces. They hatch in water and attach to snails, releasing microscopic larvae and exposing humans.

Swimmer's itch is caused by a very tiny parasite. You can only see it with a microscope. It gets into the skin of humans by mistake. The rash and itching are the body's allergic reaction to parasites ...

Both a chlorine rash and swimmer’s itch (cercarial dermatitis ... If your chlorine rash doesn’t respond to OTC treatments, speak with a healthcare professional like an allergist.