Swimmers Itch: 8 Questions & Controlling It In Lakes & Ponds

What is Swimmers Itch?

Swimmers Itch (also known as Cercarial dermatitis, Lake Itch and Duck Itch) is an itchy rash that is caused by a certain type of parasite (shistosomes) that live in freshwater snails and waterfowl that gather among lake weeds.

As part of their life-cycle, these parasites are released on warm sunny days and migrate through the water.  They then reattach to swimmers by burrowing into the skin.  Humans are not good hosts so the parasites soon die while still under the skin, which may cause an allergic reaction.

Who gets Swimmers Itch?

All age groups and both sexes can get swimmers itch.  Children are most often infected due to their habit of swimming or wading in shallow water and playing on the beach, allowing lake water to evaporate. 

How does Swimmers Itch spread?

An individual may get the infection by swimming or wading in infested water and then allowing water to evaporate off the skin rather than drying skin with a towel.  Person-to-person spread does not occur.

What are the symptoms of Swimmers Itch?

Repeated exposure increases a person’s allergic sensitivity to the parasite and increases the likelihood of rash development.  Symptoms may appear within 1-2 hours of exposure.  An initial tingling sensation may be felt associated with penetration of the parasite into the skin. The irritated raised papule, which reaches its maximum size after about 24 hours, may continue itching for several days.  Symptoms should disappear within a week.

What is the treatment of Swimmers Itch?

There is no necessary treatment.  Swimmers Itch is uncomfortable but usually short-lived and will clear within a few days.  Over-the-counter medication will normally help control itching.

When can you get Swimmers Itch?

First outbreaks usually occur in late May or early June and last up to one month.

What can be done to reduce the chances of getting Swimmers Itch?

• Toweling off immediately after swimming or wading in infested water.

• Swim in water away from the shore.

• Avoid swimming in areas where the snails have accumulated.

• Don’t encourage birds to stay near swimming areas by feeding them.

 How can I prevent or control Swimmers Itch?

• Copper Sulfate is toxic to snail hosts.  Call Aquacide Company for assistance 800-328-9350.

• Physically remove lake weeds & muck where snail gather.

• Administer praziquantel to hatchling waterfowl.

• Topical application of a water-resistant insect repellent with DEET.

• Water resistant sun cream with .1-1% niclosamide has been shown to be a highly reliable protectant

Next Steps:

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Swimmers Itch, Wikipedia, the free encyclopedia,  Swimmers Itch, Wisconsin Department of Health Services, www.dhs.wisconsin.gov, Swimmers Itch, www.MayoClinic.com/health/Swimmers-itch