Swimmer's Itch (Cercarial Dermatitis)

Swimmer’s itch is a skin rash that develops, when the larvae of certain flatworms penetrate human skin. Flatworms normally infect ducks, geese, gulls, beavers and muskrats.

Birds and animals that are infected with flatworms (schistosomes) pass eggs in their feces into ocean and fresh water. The eggs hatch and release larvae that subsequently enter snails. These larvae mature in the snail to adults and subsequently release another set of larvae (cercaria) in about a month into the water.

This cercaria is what burrows into the skin of swimmers causing an inflammatory condition resulting in rash and itching.

Where does it occur?

It occurs worldwide, the incidence is higher in summer months.

How is it transmitted?

It is transmitted when the larvae penetrate skin as humans swim in infested waters.

What is the risk for travelers?

There is a low to moderate risk for travelers who swim.

How soon after exposure will one develop symptoms?

Typically, symptoms occur within half an hour after exposure, but maybe up to a day or two later.

What are the signs and symptoms?

Typically, one sees a red rash that is similar to pimples and itchy. If one itches these lesions, they can enlarge to form ulcers and blister.

The rash is seen on exposed areas not under skin protected by clothing like bathing suits.


Are there any lab tests to diagnose the illness?

No, the diagnosis is based on symptoms, findings and history of exposure.

Is there any treatment?

Treatment is supportive, with cool compresses, calamine lotion or Benadryl cream. If the lesions are not improving, Corticosteroid creams may be beneficial.

Is the infected person contagious?

No, there is no person to person transmission of the illness.

What preventive measures can be taken?

Avoid swimming in waters known to cause swimmers itch.

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