Identifying, Treating and Preventing
Swimmer's Itch

The Full Story

Snails found in freshwater, and rarely in salt water, can be infected by juvenile parasites (cercarial larvae) that are present in the water. Infected snails can then release the larvae back into the water. When swimmers come into contact with these parasite larvae, the larvae can burrow under the skin, causing an allergic reaction that manifests as itching and rash. This is called swimmer’s itch or cercarial dermatitis. 

Swimmer’s itch is a water-borne parasitic disease, and the normal life cycle of the disease-causing parasite involves different animals. Several species of birds (geese, ducks, gulls) and mammals (beavers) that live near water can be infected with parasites in their blood. The adult parasites produce eggs, which are passed into the water from the feces of these animals. If the parasite eggs are released into or near the water, they can hatch into larvae, which can then infect snails. The larvae can be encountered by swimmers, particularly in shallow and marshy areas, although the tiny larvae are too small to see. The larvae are able to painlessly burrow into human skin, but the parasites are not able to survive there. The larvae die, but their presence in human skin can cause the characteristic itchy rash.

Within a few minutes to a couple of days after swimming in contaminated water, a rash can develop. The rash may appear similar to pimples, chickenpox, or blisters, and is often red and itchy or burning in nature. The rash typically involves areas of the body that are exposed to the water, with areas of skin covered by bathing suits being spared. This helps to differentiate swimmer’s itch from seabather’s eruption, which primarily affects the skin under the swimsuit. While the rash is uncomfortable, it is generally self-limited and not dangerous. Because it is an allergic reaction, swimmer’s itch is not contagious. Severe symptoms, including fevers, diarrhea, and nausea, are rarely reported to occur in patients with swimmer’s itch.

Most cases of swimmer’s itch can be easily treated at home. If you suspect swimmer’s itch, you should take a shower if you have not already done so after getting out of the water. Drying your skin with a towel, instead of air drying, may help remove the larvae from the skin. Cool compresses and soaking in Epsom salts or oatmeal baths can soothe the rash. Baking soda baths and pastes can be helpful as well. Topical steroids such as hydrocortisone cream and antihistamines such as diphenhydramine (Benadryl®) can be used to treat itching. More severe cases may require treatment with prescription medications. Avoid excessive scratching of the itchy areas because this can lead to a skin infection. Most cases of swimmer’s itch will resolve within 1 to 2 weeks with simple home treatment. If symptoms do not resolve or if the rash appears to be getting infected, seek medical attention.

For questions about swimmer's itch, go to poison.org or call 1-800-222-1222. Both options are free for the public, and available 24 hours a day.

Maryann Amirshahi, PharmD, MD, MPH, PhD
Medical Toxicologist