The condition known as swimmer’s itch—or cercarial dermatitis for a more technical-sounding name—can affect people who swim or wade in warm open water in most places around the world. It’s much more common in freshwater bodies like lakes and ponds, but it can occur in salt water, too. It’s not a particularly serious condition, but it’s definitely a nuisance. So, here’s what you need to know about swimmer’s itch.
Cause of Swimmer’s Itch
Cercarial dermatitis is an allergic reaction to infection by a parasite that burrows into the skin. Gross, huh? These parasites normally live in waterfowl, wading birds, and migrating birds, as well as some mammals, like raccoons, beavers, and muskrats.
Their eggs are released via an infected bird’s feces, and if they end up in the water, larvae hatch. These need to develop in snails. Once they do, the parasites exit the snail and swim around looking for a host. They will enter a human if the opportunity presents itself, but they can’t live for long or continue their life cycle in a human host.
The parasites causing swimmer’s itch are acquired in warm water, so it’s most common during summer months. You can’t spread the rash or the infection to another person or animal.
Swimmer’s Itch Symptoms
The condition presents as a red rash. It may be a patchy pinpoint rash, or look more like pimples or blisters. And it’s tingly or itchy, but usually not severely so. The rash typically only appears on skin that was directly exposed to the water, and not covered by your swimsuit or any accessories.
The itching of swimmer’s itch can begin within minutes of infection. The rash isn’t usually far behind, often appearing within a few to 12 hours, and reliably within 48 hours. Expect cercarial dermatitis to last a few days, and sometimes up to seven days.
Treating Swimmer’s Itch
Usually, no treatment is required. The parasites can’t live in a human host, so they die off while in the skin and are flushed out. See your doctor if the rash and/or itching persists for days or are severe, or if there’s pus or other signs of infection.
Symptoms are manageable with standard treatments for rash, itching, and allergic reactions. Try a cold compress on affected areas, a topical anti-itch application, a topical or oral antihistamine, bathing in Epsom salt or colloidal oatmeal, or a corticosteroid. Refrain from scratching, as this can inflame the rash and lead to secondary infections.
About Swimmer’s Itch Prevention
Chlorinated water is safe from the parasites that cause swimmer’s itch. But if you swim in warm fresh or salt water where there are mollusks and birds or host mammals, you’re at risk of contracting the infection.
There’s no way to know if water is infested with these parasites, unless of course you know that people have gotten infected after swimming in a particular body. In such cases, refrain from wading or swimming in that water.
The more time you spend in the water, the greater your chances of coming into contact with parasites if they’re in there. Also, the more skin you have exposed, the higher the risk of infection. The risk is also greater in the warmest shallow water, so swimming out to deeper water reduces your chances of catching swimmer’s itch. Wearing waterproof sunblock may also help keep the parasites out of your skin. Always rinse off thoroughly and towel dry after getting out of the water, too.
