Swimmers Itch

 What is Swimmer’s Itch?

Swimmer’s Itch, also called cercarial dermatitis, is an irritation of the skin caused by the larvae of certain parasites (Family Schistosomidae) that affect aquatic life and waterfowl. They do not parasitize humans, but do burrow into human skin trying to complete their life cycle. The larvae die shortly after enter the skin causing an allergic reaction that is “the itch”. Swimmer’s Itch is fairly common in many of the pristine lakes in our area of Northern Michigan. It also occurs in at least 30 other states as well as Canada, Europe, Africa, and Asia.


Reactions to Swimmer’s Itch vary widely. Some individuals are not noticeably affected while others develop allergic reactions that can be mild to severe. Young children and people with fair skin may be more susceptible than others. Common Symptoms include: tingling, burning, or itching of the skin and small reddish bumps or blisters. Symptoms may last up to a week or more but will gradually go away.

 How is it transmitted?

Swimmer’s itch starts out as an egg on intestinal lining of waterfowl, mostly ducks. Eggs are released into the water and hatch into “miricidia” that enter snails. Snails then release “cercaria” that swim in search of waterfowl, to complete the cycle. The cercaria causes swimmer’s itch in humans by burrowing into the skin where they quickly die. The cercaria typically inhabits shallow water which facilitates coming into contact with a duck (its definitive host. Once it’s in the duck, it easily moves around the lake, and ultimately along the shores.

The Common Merganser

(Mergus merganser) Mergansers are the primary transmitters and spreaders of Swimmer’s Itch. They are large bodied ducks that live on freshwater rivers and lakes and nest in tree cavities, often within 1/4 mile of the water.

Treatment of Swimmers Itch

Do not scratch as this can cause the rash to become more irritated or infected.

  • Use corticosteroid cream.
  • Apply cool compress to affected areas.
  • Bathe in Epsom salts or baking soda.
  • Soak in colloidal oatmeal baths.
  • Apply baking soda paste.
  • Use an anti-itch lotion.

If itching is severe a health care provider may prescribe lotions or creams to lessen symptoms.

Prevention – What Can You Do?

  • Avoid swimming in shallow water near shore where swimmer’s itch is most common.
  • Use a Swimmer’s Itch cream or waterproof sunscreen with 15 SPF or greater before entering the water.
  • Shower or towel dry rubbing vigorously after leaving the water.
  • Do not attract waterfowl to swimming areas.
  • Help educate others on the issue.
  • Volunteer to help the Avoidance Program.