Swimmer’s Itch

What is swimmer’s itch?

Swimmer’s itch, also called cercarial dermatitis, is a skin rash caused by an allergic reaction to infection with a parasite.

How is swimmer’s itch transmitted?

The microscopic parasites (which live in birds and mammals) can infect snails. These parasites, in the form of larvae, are released from infected snails to swim in fresh and salt water, such as lakes, ponds, and oceans used for swimming and wading.

Humans get swimmer’s itch when the larvae (cercarial) burrow into the skin. The larvae cannot develop inside a human and they soon die.

Who is at risk for swimmer’s itch?

Anyone who swims or wades in infested water may be at risk. Larvae are more likely to be swimming along shallow water by the shoreline.

Children are most often affected because they swim, wade, and play in shallow water more than adults. Also, they do not towel dry themselves when leaving the water.

What are the signs and symptoms of swimmer’s itch?

• Within minutes to days after swimming in contaminated water, a person may experience tingling, burning, or itching of the skin.
• Small reddish pimples appear with 12 hours.
• Pimples may develop into small blisters.
• Itching may last up to a week or more, but will gradually go away.

What is the treatment for swimmer’s itch?

The following may give relief:

• Corticosteroid cream
• Cool compresses
• Bath with baking soda
• Anti-itch lotion
• Calamine* lotion
• Colloidal oatmeal baths, such as Aveeno

Scratching may cause the rash to become infected. If itching is severe, your health care provider may prescribe lotion or creams to lessen your symptoms.

Can you get swimmer’s itch more than once?

Yes. Because swimmer’s itch is caused by an allergic reaction to infection, the more often you swim or wade in contaminated water, the more likely you are to develop more serious symptoms.

The greater the number of exposures to contaminated water, the more intense and immediate symptoms of swimmer’s itch will be.

Can swimmer’s itch be spread from person-to-person?

No.

Once an outbreak of swimmer’s itch has occurred in water, will the water always be unsafe?

No. Many factors must be present for swimmer’s itch to become a problem in water. Since these factors change (sometimes within a swim season), swimmer’s itch will not always be a problem.

However, there is no way to know how long water may be unsafe.

What can be done to reduce the risk of swimmer’s itch?

• Avoid swimming in areas where swimmer’s itch is a known problem or where signs have been posted warning of unsafe water.
• Avoid swimming near or wading in marshy areas where snails are commonly found.
• Towel dry or shower immediately after leaving the water.
  • This is important since the larvae do not penetrate the skin until the water evaporates (the towel should not be used again until it has been laundered).
• Encourage health officials to post signs on shorelines where swimmer’s itch is a current problem.
• Do not attract birds by feeding them in areas where people are swimming.

Is my swimming pool safe to swim in?

Yes. As long as your swimming pool is well maintained and chlorinated, there is no risk of swimmer’s itch.

Are there other causes of rash that may occur after swimming in fresh and salt water?

Yes.

Where can I get more information?

Contact your physician or the Southern Nevada Health District, Office of Epidemiology at (702) 759-1300.

This fact sheet, which is based on information from the Centers for Disease Control, is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

Visit the CDC's Healthy Swimming webpages for more information.