Swimmer's Itch

The parasite causing swimmer's itch is present in Isle Royale waters. Swim or wade at your own risk.

NPS / Jacob Frank

 

Swimmer’s itch (cercarial dermatitis) is a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals. These parasites are released from infected snails into water. If the parasite comes into contact with a human, it sometimes burrows into the skin causing an allergic reaction and rash.

The parasite causing swimmer’s itch is present in Isle Royale waters, particularly in warm and/or shallow areas. The abundance of swimmer’s itch varies from year to year. Swimmer’s itch may cause discomfort, but it typically clears up on its own. Swimmer’s itch does not affect purification of drinking water.

 

 

The life cycle of the parasite causing swimmer's itch.

CDC

Symptoms

• Tingling, burning, or itching of the skin.
• Small, reddish pimples.
• Small blisters.

Within minutes to days after swimming in infested water, swimmers may experience tingling, burning, or itching of the skin. Within twelve hours, small reddish pimples appear, which may develop into small blisters.

Because swimmer’s itch is caused by an allergic reaction, the more you swim or wade in infested waters, the more likely it is symptoms will develop. The greater number of exposures to infested water will result in more intense and immediate symptoms. Swimmer’s itch usually only affects exposed skin not covered by swimsuits or wetsuits.

Prevention

• Swim and wade at your own risk.
• Briskley towel dry and/or shower immediately upon leaving the water.
• Swim in water away from warm, shallow shorelines.
• Check Isle Royale Current Conditions before your trip to learn about any specific water or safety advisories.

Treatment

• Swimmer's itch is not contagious human to human.
• Swimmer's itch usually clears up on its own within a week.
• If a rash occurs, apply cool compresses to affected areas or use an anti-itch lotion.

 

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  Current Conditions

  Important park alerts, updates, and weather information for your upcoming visit.

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  For Your Safety

  As your trip gets near, use this guide to help prepare, learn what to expect, and consider how you will take responsibility for your safety.

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  Drinking Water Safety

  Boiling, or filtering AND chemical treatment, are now recommended at Isle Royale. Read best practices for purifying water here.