What Is Swimmer's Itch?
CDC says swimmer's itch, also called cercarial dermatitis, is a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals, and that the parasites are released from infected snails into fresh and salt water such as lakes, ponds and oceans. The adult parasite lives in the blood of animals such as ducks, geese, gulls, swans, muskrats and raccoons, and its eggs are passed in their feces. The Minnesota Department of Health says the larvae generally survive for 24 hours once released from the snail, but an infected snail keeps producing them for the rest of its life.
CDC says tingling, burning or itching of the skin can start within minutes to days after swimming in contaminated water, small reddish pimples appear within twelve hours, and the pimples may develop into small blisters. The Hawaii State Department of Health says it can be hard to diagnose because the rash can resemble other skin problems such as poison ivy, and there are no specific tests for it.
The New York State Department of Health says most cases get better on their own, and that over-the-counter and home remedies such as anti-itch and corticosteroid creams, cool compresses, Epsom salts, baking soda and colloidal oatmeal baths can help soothe symptoms. To avoid it, the department advises not swimming or wading in water with waterfowl, snails or weeds, avoiding cloudy water, blooms and scum, and towel drying thoroughly after contact with water. CDC says a well maintained, chlorinated swimming pool carries no risk of swimmer's itch, because the right snails must be present for it to occur.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Government sourceCDC says swimmer's itch, or cercarial dermatitis, is a rash caused by an allergic reaction to microscopic parasites released from infected snails into lakes, ponds and oceans. CDC ↗
- Government sourceCDC says tingling, burning or itching can start within minutes to days after swimming in contaminated water, with small reddish pimples within twelve hours that may blister. CDC ↗
- Government sourceCDC says the adult parasite lives in the blood of animals such as ducks, geese, gulls, swans, muskrats and raccoons, and its eggs pass in their feces. CDC ↗
- Government sourceCDC says a well maintained and chlorinated swimming pool carries no risk of swimmer's itch, because the right snails must be present. CDC ↗
- Government sourceThe New York State Department of Health says most swimmer's itch cases get better on their own, and anti-itch creams, cool compresses and oatmeal baths can help soothe symptoms. New York State Department of Health ↗
- Government sourceThe New York State Department of Health advises not swimming or wading in water with waterfowl, snails or weeds, and towel drying thoroughly after contact with water. New York State Department of Health ↗
- Government sourceThe Minnesota Department of Health says swimmer's itch larvae generally survive for 24 hours after leaving the snail, but an infected snail keeps producing them for life. Minnesota Department of Health ↗
- Government sourceThe Hawaii State Department of Health says swimmer's itch can be hard to diagnose because the rash resembles other skin problems, and there are no specific tests for it. Hawaii State Department of Health ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.