What Is Swimmer's Itch? - Verywell Health

Swimmer's itch (cercarial dermatitis) is a noncontagious rash caused by a parasite in water. It's common in people who swim or wade in fresh water, such as ponds or lakes. It's less common, but still possible, to catch it in ocean water.

Snails, waterfowl, beavers, and other aquatic birds and animals can become infected with the cercaria parasite. Cercaria eggs are then passed into the water through feces (poop). 

This article discusses the symptoms, causes, diagnosis, and treatment options for swimmer's itch.

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Swimmer's Itch Symptoms

The typical symptoms of swimmer's itch include:

• Tingling, itching, or burning skin
• Small discolored pimples
• Small blisters

Skin Color Differences

Your skin color can affect the appearance of a rash. Rashes that look pink or reddish on light skin may appear pink, purplish, darker, or lighter shades than the skin or simply like bumps with no discoloration.

How Long Does It Take to Get Swimmer's Itch?

The longer you're in the contaminated water, the more likely you are to come into contact with the larvae. Symptoms of swimmer's itch can start anywhere from a few minutes to a few days after you swim, but it often begins within two hours of swimming.

The tingling, itching, or burning sensations start first, followed by pimples in about 12 hours. The pimples may develop into small blisters. You may be itchy for a week or longer.

The more often you go into contaminated water, the more likely you will develop symptoms quickly. Repeated exposure may also make the symptoms more intense.

Causes

An allergic reaction to cercarial larvae causes swimmer's itch. The cercarial eggs pass into the water through the feces of infected animals.

After they hatch, the larvae burrow into your skin, creating an itchy rash. Humans aren't good hosts for them, so they die off before long, which means not everyone who enters water will get swimmer's itch—you must have an allergy to the larvae. (The ideal host is a duck.)

It also means swimmer's itch isn't contagious, so you don't have to worry about giving it to (or getting it from) people around you. You may develop the allergy and the rash it leads to after repeated exposure to the cercarial larva.

Swimmer's Itch in Kids

Children are more likely than adults to develop swimmer's itch. This is partly because they tend to stay in shallow water, which is more likely to contain larval parasites.

How Do I Know if I Have Swimmer's Itch?

Swimmer's itch is usually easy to identify from its symptoms and how it progresses (itching, pimples, and blisters). The rash only affects areas of skin that are directly in contact with the water and will not spread to other areas, even if you scratch it. It's most common in areas not covered by a swimsuit or wetsuit.

Water Rashes

Swimmer's itch isn't the only rash you can catch from natural bodies of water. Other rashes include:

• Cyanobacterial (blue-green algae) rash: Large, itchy, discolored patches with broken skin
• Pseudomonas rash: A bacterial infection that looks similar to swimmer's itch but may have a white dot in the middle of each discolored bump
• Seabather's eruption: Very itchy rash caused by hypersensitivity to jellyfish larvae. Appears under the swimsuit after extended exposure

You can't catch swimmer's itch from a swimming pool. However, you may develop a chlorine rash, which is a type of irritant dermatitis. It causes itchy hives.

How Can I Prevent Swimmer's Itch?

You can lower your risk of developing swimmer's itch by:

• Towel-drying immediately after getting out of the water
• Showering right away
• Not swimming in areas where it's a known problem or warning signs are posted
• Not going into marshy areas, which often have a high snail population
• Not feeding birds around swimming areas as it can increase the amount of feces—and therefore parasites—in the water

If you get swimmer's itch, let a health official know. They may want to post warning signs to protect other people.

How Can I Get Rid of Swimmer's Itch?

Most cases of swimmer's itch can be treated at home. Your options for soothing the rash include:

It may also help to take an antihistamine (allergy pill).

When to Get Medical Help for Swimmer's Itch

Some cases of swimmer's itch do need medical attention. Make an appointment with your healthcare provider if:

• The itching is severe and doesn't improve after 24 hours of using a corticosteroid cream.
• You have a scab that gets bigger or oozes pus.
• The rash lasts for more than two weeks.

Get immediate medical care if you notice:

• Red streaks moving away from the area
• A fever
• A rash that's spreading
• Your child appearing very sick

Also seek care if you've had severe post-swimming reactions in the past that required oral steroid treatment.

Widespread Problem

The parasite that causes swimmer's itch is found in all 50 states but is most common in the Great Lakes region (Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, New York, and Michigan, and Ontario in Canada). It's also found in other parts of Canada and in more than 30 other countries.

Prognosis

Your first case of swimmer's itch may last up to two weeks. If you avoid infection, it should clear up without complications or lingering symptoms.

However, it's important to remember swimmer's itch is caused by an allergy. Each time you get swimmer's itch, it will likely be more severe than the last. Be sure to take precautions to prevent future exposure to the parasites.

Summary

Swimmer's itch is an allergic reaction to a parasite in fresh water like ponds or lakes. It's more common in children than adults. It causes an itchy, discolored rash that may look like pimples or small blisters. It's not contagious.

You can prevent swimmer's itch by towel drying and/or showering right after leaving the water and avoiding areas of likely or known contamination. The rash can be treated with corticosteroid or anti-itch creams and baths with soothing ingredients. Repeated cases tend to be more severe.

By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.

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