Swimmer's Itch

Swimmer's Itch

Last Updated: July 1, 2021
HealthLinkBC File Number: 52
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What is swimmer's itch?

Swimmer's itch is a skin rash caused by an allergic reaction to small worm-like parasites called schistosomes (shiss-toe-soams). Schistosomes spend their life cycle as parasites in the bodies of water snails and in the blood stream of aquatic mammals, ducks or other waterfowl. During their life cycle, schistosome larvae (called cercariae) leave their snail host and swim near the surface of the water, looking for bird and mammal hosts.

How can I get swimmer’s itch?

If schistosome larvae are present in a body of water and you are in that water (swimming or wading) there is a chance that one or more larvae will burrow under your skin. Since the larvae cannot survive in humans they will die almost immediately. It is the reaction to these tiny parasitic larvae under the skin that causes swimmer’s itch.

Swimmer’s itch cannot be spread from person to person.

Where are these parasites found?

Schistosomes are found in many lakes, ponds and coastal waters in British Columbia, usually in the warm summer months. Their larvae are more likely to be found floating near the surface in shallow water along the shores of fresh waters and coastal beaches.

Cases of swimmer’s itch have been reported across Canada, including in B.C., and the northern United States.

Who has a higher risk of getting swimmer’s itch?

Young children who wade and splash in shallow water bodies may be at higher risk because:

  • They are constantly getting wet without thoroughly drying off
  • They usually play by the shore where the presence of schistosomes and their larvae is higher
  • Younger children’s skin can be more sensitive than the skin of an adult

How can I avoid swimmer's itch?

There is no sure way to avoid swimmer’s itch entirely unless you avoid water bodies. However, there are certain precautions you can take:

  • Speak with other visitors to the area, local health officers or parks representatives about the water condition before getting in any lake, pond or beach
  • Check for warning signs at public beaches, lakes and picnic areas for notices stating that swimmer’s itch may be present. Not all beaches have signage for swimmer’s itch. If you are unsure about the water, avoid areas with lots of weed growth. There may be more snails and larvae around aquatic plants
  • Use a pier or dock to enter the water to help reduce your risk of exposure, as there may be more larvae near the shore. Make sure these structures are approved for swimming and do not dive into unknown waters. See HealthLinkBC File #39 Safety Tips for Swimmers or contact the Lifesaving Society at www.lifesaving.bc.ca for more information on swimming safety and drowning prevention
  • Dry yourself off with a towel as soon as you come out of the water. If possible, have a shower and dry off right away. However, showering will not remove any larvae that have already burrowed under your skin

What are the symptoms?

Symptoms can range from a mild irritation to a very severe, itchy red rash. Scratching can cause severe pain and swelling or cause your skin to become infected. The severity of your symptoms will depend on how many larvae get on to your skin, and how sensitive you are to them. Symptoms tend to be worse after repeat exposure.

As you start to dry off and the larvae start to burrow into your skin, you may feel a tingling sensation. Small, pin sized red spots will appear, which grow into larger red rashes within several hours. As these red spots grow, the tingling feeling becomes a strong itch.

How long do the symptoms last?

A rash may appear within 12 hours after infection. The reaction may last from 2 to 5 days and symptoms can last as long as 2 weeks.

Repeat infections are usually worse. People become more sensitive to the larvae and develop stronger responses each time.

How do I treat swimmer's itch?

There are some steps you can take that may reduce some of the itchiness. Check with your health care provider about what treatment is right for you.

Common treatments and advice include:

  • Apply plain calamine lotion
  • Take antihistamines. For children, consult your health care provider such as your local pharmacist, family doctor or HealthLink BC. Antihistamines may make young children sleepy. Antihistamines may stimulate the nervous system, causing hyperactivity
  • Take shallow, lukewarm baths with 3 tablespoons of baking soda in the water
  • Take colloidal oatmeal baths
  • Apply cool compresses
  • Avoid scratching. If you scratch too much the rash may become infected

Is swimmer’s itch dangerous?

The rash and itch can be very irritating, especially for young children, but there should not be any serious danger. However, if a skin infection occurs from too much scratching, you should see your health care provider.

For More Information

For more information on swimmer’s itch, see the Ministry of Environment’s brochure at www2.gov.bc.ca/gov/content/environment/air-land-water/water/water-quality.