Swimmer's Itch (also known as Cercarial Dermatitis) 

What is swimmer's itch?

Swimmer's itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals. These parasites are released into fresh and salt water (such as lakes, ponds, and oceans). While the parasite's preferred host is the specific bird or mammal, if the parasite comes into contact with a swimmer, it burrows into the skin causing an allergic reaction and rash. Swimmer's itch is found throughout the world and is more frequent during summer months.


Symptoms usually persist for a few days up to two weeks
  • tingling, burning, or itching of the skin
  • small reddish pimples
  • small blisters


Most cases of swimmer's itch do not require medical attention. Swimmer’s itch is most commonly treated with topical creams or lotions to relieve itching. Scratching the lesions can result in secondary infection. Swimmer’s itch lesions can be confused with other causes of dermatitis such as poison ivy, chickenpox, and impetigo.


  • Avoid wading or swimming in shallow water areas of lakes or ponds, especially in marshy areas with submerged vegetation as this is a habitat where snails are commonly concentrated. 
  • Towel dry or shower immediately after leaving the water. 
  • Immediately exit the water if you feel sensations of tingling or burning on the surface of submerged skin. Immediately dry-off with a towel 
Healthcare providers should report suspected cases of swimmer’s itch to the Maricopa County Department of Public Health at 602-506-6767 so that areas of risk can be monitored and posted as necessary.

Want to know more? Visit the CDC's Swimmer's Itch FAQs page.