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What is swimmer's itch and how is it treated?

Swimmer's itch is a rash that can develop after people swim or wade in contaminated water. Certain microscopic parasites in the water can attach to the skin and cause irritation. These parasites can live in both salt and fresh water worldwide and usually infect people in the summer months.

The symptoms of swimmer's itch include itching, burning skin, and a rash. These symptoms typically begin a few hours after a swim, and are followed by redness that develops 12 or more hours later. In some cases, small pus-filled blisters develop two to three days after infection and last for several days.

Swimmer's itch generally clears up without treatment, but the irritating and uncomfortable symptoms can last up to two weeks. To soothe the symptoms, try an oral antihistamine, such as diphenhydramine (brand name Benadryl), or hydrocortisone cream (>Cortaid or >Cortizone). You can also try cool compresses and >calamine lotion.

Contact your doctor if the itching and redness do not improve within a few days or if they get worse. There is an antiparasitic medication available called praziquantel (Biltricide) if your doctor feels it is necessary.

To avoid infection, don't swim in areas where swimmer's itch is a known problem. Also, shower with clean water after swimming in lakes, rivers, streams, or the ocean. If a shower is not available, towel drying immediately after leaving the water may also help prevent swimmer’s itch. Avoid bodies of water that are home to a high concentration of birds, since waterfowl such as ducks, geese, gulls, and swans can carry the parasites.

Sources:
Cercarial dermatitis." Centers for Disease Control and Prevention, www.cdc.gov, last accessed 7/2001.
American Academy of Pediatrics Red Book: Report of the Committee on Infectious Diseases. American Academy of Pediatrics, 1997.
Drug Facts and Comparisons. Facts & Comparisons, 2006.
Habif, Thomas. Clinical Dermatology. Mosby-Year Book Inc., 1996.
Handbook of Nonprescription Drugs. American Pharmaceutical Association, 2000.
Hoeffler, D.F. “Swimmer's itch (Cercarial Dermatitis)," Cutis 4 (1977).
Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Churchill Livingstone, Inc., 1996.
Medline Plus. Medline, 2006.
Micromedex® Healthcare Series. Thomson Micromedex, 2006.

This answer prepared 7/2/2001.
This information updated 1/25/2007.