Columbia River giving swimmers the itch. What to watch out for in Tri-Cities

Swimmer’s itch is making some people who have played in shallow areas of the Columbia River miserable this summer, says the Benton Franklin Health District.

The itch, also called cercarial dermatitis, is caused by an allergic reaction to certain microscopic parasites that burrow into the skin through pores.

Symptoms can include:

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

The temptation is to scratch, which can cause secondary bacterial infections.

“This condition isn’t contagious and usually goes away on its own, but it can be very uncomfortable,” said Dr. Steve Krager, health officer for Benton and Franklin counties.

“We want people to be aware and take a few simple precautions to reduce their risk while enjoying the water,” he said.

The adult parasite lives in the blood of infected animals or birds, which in the Tri-Cities area includes ducks and geese. Their eggs contaminate the birds’ droppings, according to the Centers for Disease Control and Prevention.

The eggs hatch in the water, releasing small, free-swimming microscopic larvae that search out snails to infect. They multiply and develop in the snail, before being released as a different type of microscopic larvae in the water to repeat the lifecycle.

They search out a bird or mammal as a host, but can mistakenly burrow into human skin where they do not survive.

The condition is not contagious, so there is no requirement that medical professionals report it to the health district. But district health professionals have heard anecdotal reports of swimmer’s itch this month.

At least one report was linked to playing in shallow river water in a Richland park where ducks or geese gather.

Health officials recommend not feeding ducks or geese in areas where people swim, and staying out of marshy areas where snails are often found.

Children are most often affected by swimmer’s itch, since they tend to wade and play in shallow water, according to the CDC.

They also are less likely to towel dry themselves after being in the water.

To prevent the larvae from burrowing into skin, showering or towel drying is recommended immediately after leaving the water.

Sunscreen applied before going into the water also can help prevent swimmer’s itch by blocking the skin’s pores.

Treating swimmer’s itch

Symptoms may appear within minutes of swimming in contaminated water and itching may last for up to a week or more before it gradually goes away, according to the CDC.

Because the itch is related to an allergic reaction, the more often people are exposed to contaminated water, the more intense and immediate the symptoms, it said.

Most cases don’t require medical attention. But to relieve the itch, the CDC recommends:

• Use corticosteroid cream
• Apply cool compresses to the affected areas
• Bathe in Epsom salts or baking soda
• Soak in colloidal oatmeal baths
• Apply baking soda paste to the rash (made by stirring water into baking soda until it reaches a paste-like consistency)

If itching is severe, a health care provider may recommend a prescription-strength lotion or cream.

The snails that are associated with swimmer’s itch can live in fresh or salt water. But there is no risk of swimmer’s itch in a well maintained and chlorinated swimming pool.

This story was originally published July 21, 2025 at 6:37 PM.