Swimmer’s Itch

Water bodies with large numbers of ducks, geese, and snails also provide habitat for the flatworms that cause swimmer’s itch. July and August are typically the months the Health Department begins receiving complaints about swimmer’s itch. “When we receive a complaint from beach users who have swimmer’s itch, Health Department staff post warning signs at the beach and notify the beach owner,” Madison said. “So reporting swimmer’s itch to the health department is important.”

Swimmer’s itch, also known medically as cercarial dermatitis, is caused when tiny larval flatworms enter a bather’s skin while the person is swimming. The flatworm is unable to enter human blood vessels, and therefore, dies in the skin. Some people can have an allergic reaction to the parasite and suffer itchy, redden, raised areas on their skin with symptoms lasting for about a week. The condition is self-limiting because the immune system takes care of the intruders and the itchy rash simply disappears after that. However, at the peak of symptoms, corticosteroid cream and an oral antihistamine drug may be needed to control the itch.

The usual hosts for the flatworms that cause swimmer’s itch are ducks, geese, and snails. The flatworms also have a free-swimming stage in fresh water lakes. During July and August, swimmers can be exposed to large numbers of these flatworms along shorelines. Swimming in areas with large water fowl populations and snails should be avoided.

For additional information about swimmer’s itch, please visit our Seasonal Health Topics.