Swimmer’s itch is a rash caused by an allergic reaction to the larvae of microscopic parasites that are found in both fresh and saltwater. These parasites commonly live in snails, which secrete larvae into the water, per the CDC. 

Swimming in contaminated water for even a short period of time can cause swimmer’s itch, and after you come in contact with the larvae, “when the skin dries off, those parasites burrow under people's skin and cause an itchy rash,” says Dr. Christina Boull, MD, an associate professor of dermatology and pediatrics at M Health Fairview University of Minnesota Medical Center. Read on to learn what symptoms to look out for and precautions you can take to prevent this uncomfortable summertime rash.

What is swimmer’s itch?

You can identify swimmer’s itch, also known as cercarial dermatitis, from the little red dots that appear on your skin after you’ve been exposed to the parasites, Boull says. The rash will likely manifest on skin that was directly exposed to the water as opposed to skin protected by your bathing suit. For this reason, your arms and legs are particularly vulnerable to swimmer’s itch, she says. 

These dots typically appear 12 hours after exposure, and over the next day or two, some people may experience a more severe reaction with welts and blisters. “One of the main risk factors of complication from this rash would be a secondary bacterial infection.” If you scratch the rash, there’s a possibility of staph bacteria getting under your skin, leaving your body vulnerable to developing staph infections such as impetigo or cellulitis, she says.

What can be mistaken for swimmer’s itch?

When it comes to swimming in the ocean, seabather’s eruption is a rash that presents similar symptoms to swimmer’s itch. In terms of identifying whether your rash is swimmer’s itch or sea bather’s eruption, the latter tends to develop under a swimsuit, Boull explains. Comparatively, swimmer’s itch is more likely to appear in areas that are not protected by a swimsuit, she reiterates.

Additionally, because swimmer’s itch presents as small red bumps, it is also commonly mistaken as bites caused by small bugs, such as gnats or mosquitoes, Boull says.

How do you get rid of swimmer’s itch?

“The good news is that it spontaneously resolves,” Boull says. Because people are the preferred hosts of the mites, they don’t live in the skin very long. Typically, the rash and itch significantly improves over the course of a week, although it’s possible for it to last as long as three weeks, she says.

To quell the itching of the rash, Boull suggests 1% hydrocortisone, an over the counter topical steroid cream. She also recommends taking an oral antihistamine.

In cases of severe itch, prescription oral prednisone and oral cortisone medicines can help relieve itch and inflammation.

If your swimmer’s itch has developed into blistering, open sores, and you’re experiencing fever, it could be signs of the secondary bacterial infection. In this case, it’s essential you see a doctor who can prescribe you oral antibiotics, Boull says.

Does showering prevent swimmer’s itch?

The parasites that cause swimmer’s itch can only burrow into your skin after you’ve dried off. “So, it's really important after getting out of a lake or areas where you're swimming that would have snails, that you take a towel and really wipe the water off your skin.” Showering after you’ve gotten out of the water can also help to prevent the parasites from getting underneath your skin. 

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Snails tend to prefer warm, shallow water, so avoiding these areas can limit the possibility of exposure to the parasites. Finally, take note of no swim zone signs that may indicate whether there are pathogens in the water.