Identifying, Treating and Preventing
Swimmer's Itch

group jumping off a boardwalk into a lake

The Bottom Line

Swimmer’s itch occurs when your body has an allergic reaction to parasite larvae found in swimming water. While the rash maybe uncomfortable and is often very itchy, it usually resolves with simple home treatment.

man itching his arm

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

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Prevention Tips

  • Do not feed birds in areas where people swim. 
  • Avoid swimming in marshy or shallow waters whenever possible, as there are more snails in these areas. 
  • Avoid swimming in areas where posted signs warn that swimmer’s itch is a problem.
  • Prolonged time in water is a risk factor for swimmer’s itch and may result in more severe symptoms.
  • Towel dry and shower immediately after leaving the water. 
  • Apply waterproof sunscreen as this may protect the skin from larvae that cause swimmer’s itch. 

This Really Happened

A 41-year-old woman went swimming in a lake where there was a lot of vegetation present near the water surface. The next day, she developed an itchy rash on her face and shoulders. Her skin felt hot and she noticed the symptoms were worse in the morning. She went to her primary care doctor who recommended use of oral antihistamines and moisturizing lotion. She also saw a dermatologist who performed a skin biopsy that revealed the presence of cercariae within the skin. This confirmed the diagnosis of swimmer’s itch. She was treated with prescription antihistamines and topical steroid cream and the rash completely resolved within 2 weeks. 

References

CDC. Parasites - Cercarial Dermatitis (also known as Swimmer's Itch). [accessed 11/11/21].

Chamot E, Toscani L, Rougemont A. Public health importance and risk factors for cercarial dermatitis associated with swimming in Lake Leman at Geneva, Switzerland. Epidemiol Infect 1998:120:305-4.

Hoeffler DF. “Swimmers’ itch” (cercarial dermatitis). Cutis 1977;19:461-7.

Tremaine AM, Whittemore DE, Gewirtzman AJ, Bartlett BL, Mendoza N, Rapini RP, Tyring SK. An unusual case of swimmer’s itch. J Am Acad Dermatol 2009;60:174-6. 

Verbrugge LM, Rainey JJ, Reimink RL, Blankespoor HD. Prospective study of swimmer’s itch incidence and severity. J Parasitol 2004;90:697-704.

Poisoned?

Call 1-800-222-1222 or

HELP ME online

Prevention Tips

  • Do not feed birds in areas where people swim. 
  • Avoid swimming in marshy or shallow waters whenever possible, as there are more snails in these areas. 
  • Avoid swimming in areas where posted signs warn that swimmer’s itch is a problem.
  • Prolonged time in water is a risk factor for swimmer’s itch and may result in more severe symptoms.
  • Towel dry and shower immediately after leaving the water. 
  • Apply waterproof sunscreen as this may protect the skin from larvae that cause swimmer’s itch. 

This Really Happened

A 41-year-old woman went swimming in a lake where there was a lot of vegetation present near the water surface. The next day, she developed an itchy rash on her face and shoulders. Her skin felt hot and she noticed the symptoms were worse in the morning. She went to her primary care doctor who recommended use of oral antihistamines and moisturizing lotion. She also saw a dermatologist who performed a skin biopsy that revealed the presence of cercariae within the skin. This confirmed the diagnosis of swimmer’s itch. She was treated with prescription antihistamines and topical steroid cream and the rash completely resolved within 2 weeks.