What is swimmer's itch?

Swimmer's itch is a rash caused by an allergic reaction to the larvae of certain parasites. A parasite is an animal or plant that lives in or on another animal or plant (called the host). The rash looks like reddish bumps on the skin. It often appears outside the bathing suit. How severe the rash is may vary for people exposed to the same parasites.

The parasites can get under your skin when you swim in fresh water (such as lakes and ponds) and sometimes in salt water. This causes an allergic reaction and an itchy rash. The itching is worse in the first few days after it starts. Then it gets better after about a week. Because the parasite can't live in the human body, swimmer's itch goes away on its own.

You don't get swimmer's itch from swimming pools that are treated with chlorine. And it doesn't spread from person to person.

Symptoms of swimmer's itch include:

• A rash that usually goes away in about a week.
• An itching or burning feeling on your skin.
• Bumps on your skin that show up minutes or even days after you were in the water. The bumps may later turn into blisters.

How severe the rash is may vary for people exposed to the same parasites.

In most cases, swimmer's itch goes away on its own, so you don't need to see a doctor.

To treat the itching at home, you can:

• Put cool wet cloths (compresses) on your skin.
• Use anti-itch creams that you can buy without a prescription in a grocery store or drugstore.
• Put calamine lotion on your skin.
• Add a handful of oatmeal (ground to a powder) to your bath. Or you can try an oatmeal bath product, such as Aveeno.

Try not to scratch the rash. This could lead to an infection.

To lower your chance of getting swimmer's itch:

• Don't go near lakes or ponds that are known to have outbreaks of swimmer's itch.
• Shower or dry yourself off with a towel as soon as you get out of a lake or pond.

A doctor can diagnose swimmer's itch by looking at your skin and asking if you've been swimming in ponds or lakes.

If your skin itches

• Put cool, wet cloths (compresses) on your skin.
• Put calamine lotion on your skin.
• For a short time, use an anti-itch cream like hydrocortisone that you can buy without a prescription in a grocery store or drugstore.
• Take an over-the-counter antihistamine. Be safe with medicines. Read and follow all instructions on the label.
• Add a handful of Epsom salts, baking soda, or oatmeal (ground to a powder) to your bath. Or you can try an oatmeal bath product, such as Aveeno.

To help prevent swimmer's itch

• Avoid lakes or ponds that are known to have outbreaks of swimmer's itch.
• Shower as soon as you get out of a lake or pond.
• Dry off briskly with a towel.

Swimmer's itch is a rash caused by an allergic reaction to the larvae of certain parasites. The parasites can get under your skin when you swim in freshwater (such as lakes and ponds) and sometimes salt water. But you can't get swimmer's itch from swimming pools that are treated with chlorine.

The tiny parasites infect birds or mammals and lay eggs. Bird and mammal droppings that contain the eggs get into lakes and ponds. The eggs hatch into larvae, which then infect snails. The snails in turn release the larvae into the water, where the larvae look for a host. If they come in contact with people, the parasites can burrow under the skin. This causes an allergic reaction and a rash.

But the larvae can't survive in humans, so the parasites die. As a result, the rash usually goes away on its own and doesn't need treatment. The rash can't be spread from person to person.