Swimmer’s itch is an itchy rash that can occur after you go swimming or wading outdoors. Also known as cercarial dermatitis, swimmer’s itch is most common in freshwater lakes and ponds, but it occasionally occurs in salt water.
Swimmer’s itch is an allergic reaction to microscopic parasites that burrow into your skin. The parasites associated with swimmer’s itch normally live in waterfowl and some animals that live near the water. Humans aren’t suitable hosts, so the parasites soon die while still in your skin.
Although uncomfortable, swimmer’s itch is usually short-lived. The rash typically clears up on its own within a few days. In the meantime, you can control itching with over-the-counter or prescription medications.
The itchy rash associated with swimmer’s itch looks like reddish pimples or blisters. It may appear within minutes or days after swimming or wading in infested water.
Swimmer’s itch usually affects only exposed skin — skin not covered by swimsuits, wet suits or waders. Signs and symptoms of swimmer’s itch typically worsen with each exposure to the parasites.
When to see a doctor
Talk to your doctor if you have a rash after swimming that lasts more than one week. If you notice pus at the rash site, consult your doctor. You might be referred to a doctor who specializes in skin conditions (dermatologist).
The parasites that cause swimmer’s itch live in the blood of waterfowl and in animals that live near ponds and lakes. Examples include:
The parasite’s eggs enter the water via their hosts’ feces. Prior to infecting birds, animals or people, the hatched parasites must live for a time within a type of snail. These snails live near the shoreline, which explains why infections occur most often in shallow water.
Swimmer’s itch isn’t contagious from person to person, so you don’t need to worry about catching swimmer’s itch from someone who has this itchy rash.