Medically reviewed by Jennifer Wong, DO
You take a dip in a cold, sparkling lake on a hot summer day, expecting to come out feeling cool and refreshed. But within minutes of wading out of the water, you find yourself with itchy legs and perhaps, small red spots. It could be swimmer’s itch, a reaction to parasites in water.
Swimmer’s itch is common throughout the world. For most people, it isn’t serious and goes away on its own. Until it does, however, it can be unpleasant.
What is swimmer’s itch?
Swimmer’s itch, or cercarial dermatitis, is an allergic reaction to cercariae, the tiny larvae of parasites called trematodes. They are typically found in fresh water, though they can be present in ocean water, too.
The larvae infect aquatic snails, then multiply and develop in them. When they are released by the snails, they infest the surrounding water looking for certain water birds or mammals to infect as part of their lifecycle. If a human happens to bump into them, the larvae may burrow into their skin by mistake. It’s unfortunate for the larvae, which can’t survive in humans and die soon after taking up residence. But until that happens, the person who’s hosting them will likely have to contend with a bout of swimmer’s itch.
Little kids are especially prone to developing swimmer’s itch since they can play for hours in shallow waters by the shoreline. It’s more common to see larvae there than offshore.
What does swimmer’s itch look like?
Swimmer’s itch symptoms include itching and a rash that often appears on the legs, since they get the most exposure during swimming or wading.
Symptoms appear in two stages:
- Tingling, burning, tenderness and itching can occur within minutes after a person exits the water.
- A rash made of small reddish pimple-like bumps appears within 12 hours. The rash may appear in a matter of minutes if you’ve been exposed to the larvae before. The bumps may increase in size and turn into small blisters.
Unlike certain other rashes, the swimmer’s itch rash doesn’t spread to other areas of the skin, and it’s not contagious.
How long does swimmer’s itch last?
Swimmer’s itch typically lasts several days to a week or even two weeks.
Swimmer’s itch treatment: Home remedies
Wondering how to get rid of swimmer’s itch? There’s no medication designed specifically to treat it. Treating swimmer’s itch comes down to soothing the irritation and itching so you aren’t tempted to scratch. (Aggressive scratching can lead to an infection.) These home remedies can help:
- Soothe it with a cold compress. Apply a cold, wet washcloth or an ice pack covered in a dish towel to itchy skin for 5 to 10 minutes at a time.
- Smooth on a cooling, calming lotion. Lotions that contain calamine or menthol have a cooling effect on skin, especially if you store them in the fridge between applications.
- Try a therapeutic soak. Add Epsom salts or colloidal oatmeal to a lukewarm bath. Colloidal oatmeal is available in drugstores, the pharmacy sections of supermarkets and big box stores and online.
- Apply an anti-itch paste. Create a thin paste with water and baking soda and apply it to the rash.
- Medicate it. Apply an over-the-counter corticosteroid cream or a product that contains a topical anesthetic such as pramoxine.
See your dermatologist if the rash does not resolve or the itching is not controlled well with at-home treatments. The dermatologist can prescribe a stronger itch-fighting medication.
How to prevent swimmer’s itch
Given the possibility of parasites in water, you may be wondering, is it safe to swim in lakes (or ponds)? If your concern is swimmer’s itch the answer is yes—sometimes. There are signs of possible cercariae infestation you can look out for when choosing where to swim, and things you can do to lower the risk of swimmer’s itch if you swim or wade in water that may be infested.
- Steer clear of lake or pond water that’s murky, scummy, weedy or cloudy.
- Avoid swimming in water where waterfowl live, and don’t swim if signs are posted that warn about the presence of snails or parasites.
- Don’t feed birds in areas where people swim. Seagulls, geese, ducks and other birds may have parasite eggs in their excrement.
- Stay away from marshes, which snails love.
- Dress small children in swimwear that includes swim tights or pants.
- If you’re a strong swimmer, get out of the shallows and head to deeper water.
- After swimming, wading or walking in water that might have larvae in it, rinse with fresh water and dry off with a clean towel to brush off any larvae that may be trying to burrow into your skin.
If you don’t manage to protect yourself from swimmer’s itch and you wind up with the telltale itchy bumps, do what you can to prevent others from getting it by alerting your local health department.
Written by Maura Rhodes, a writer and editor specializing in health and well-being.