Swimmer's itch is a skin rash caused by an allergic reaction to a parasite found in certain birds (ducks, geese, gulls, swans ) and mammals (muskrats and beavers). The parasite is passed in water from infected animal feces to a certain type of snail. The snails in turn release a different lifecycle stage of the parasite that searches for a bird or mammal to infect so they can start their lifecycle over again. The parasite does not prefer humans, but will burrow into a swimmer's skin. Because they cannot develop inside a human, they soon die.

When the parasite gets into human skin, it may cause an allergic reaction and rash.

• The rash takes several hours to appear. Generally, itching starts in the middle of the night, or about 10 hours after exposure .
• The rash continues for (10) days and gradually tapers off.
• Most cases do not require medical attention. You can use a corticosteroid cream or anti-itch lotion to relieve the discomfort.
• Swimmer's itch cannot be spread from person-to-person.

To reduce your chance of developing swimmer's itch:

• Avoid swimming in areas that have signs advising against it.
• Avoid swimming or wading in areas where there are snails.
• Towel dry (or shower) immediately after leaving the water. Towel dry frequently, especially the legs and torso. The parasite will die in a short time out of water.
• Avoid attracting birds (feeding them) to swimming areas.

Many lake associations treat local lakes with copper sulfate to kill the snails that are host to the parasite. If you would like to know if a lake has been treated, contact the city, township or village or the lake association. (Regardless, it is always a good preventive measure to towel dry immediately after swimming in case a snail survived.)

Additional Information

Swimmer's Itch Fact Sheet (CDC)