Swimmer’s Itch

Swimmer’s itch (cercarial dermatitis) is a temporary, non-contagious itchy rash that appears on your skin and is caused by a certain parasite found in fresh water (lake or pond water) or salt water (ocean water). If you swim in water that’s infested with the parasite, it can burrow (dig) into your skin. Your body has an allergic reaction to it, causing a rash. The parasites cannot survive in human skin, so they die shortly after burrowing into your skin. The rash usually gets better after a few days, but it can last for up to two weeks.

What kind of parasites cause swimmer’s itch (cercarial dermatitis)?

The parasite larvae that cause swimmer’s itch are known as cercariae. The parasites that cause swimmer’s itch originate from infected birds that live near water, such as ducks, geese and gulls, and mammals like beavers, muskrats and raccoons. The parasites lay eggs in the infected animal’s blood and then the eggs are passed through the infected animal’s poop.

If those eggs reach water, they hatch and release tiny, microscopic larvae. These larvae swim around the water looking for a certain species of snail, and if they come into contact with the snail, the larvae will multiply and further develop. Infected snails then release a different kind of larvae known as cercariae, which is why swimmer’s itch is called cercarial dermatitis. This kind of larvae then swims to the surface of the water looking for certain birds or mammals to continue the cycle.

Even though the larvae cannot survive in a human’s body, they can burrow into a swimmer’s skin and trigger an allergic reaction that causes an itchy rash, known as swimmer’s itch. The larvae soon die after they burrow into a person’s skin, but the itching and rash from the allergic reaction can last for several days.

What does swimmer’s itch (cercarial dermatitis) look like?

Swimmer’s itch (cercarial dermatitis) looks like a rash with reddish bumps or pimples. It may also cause small blisters on the skin and itch or burn. Swimmer’s itch can only appear on skin that has had contact with infested water.

How common is swimmer’s itch (cercarial dermatitis)?

Swimmer’s itch (cercarial dermatitis) is a common condition. It happens around the world and is more frequent in summer months when people are more likely to swim. Getting swimmer’s itch from fresh water, like lakes and ponds, is more common than getting it from salt water (the ocean).

Who gets swimmer’s itch (cercarial dermatitis)?

Swimmer’s itch can happen to anyone who swims in water that is infested with the parasites that cause swimmer’s itch. Young children are more likely to get swimmer’s itch because they are more likely to wade and play in shallow water where the parasites are more likely to be found.

Where on my body can I get swimmer’s itch (cercarial dermatitis)?

You can get swimmer’s itch on your body anywhere that the parasites from the infested water have come into contact. The legs are a common area to get swimmer’s itch since they are the part of your body that is most likely to be in the water, whether you are walking, wading or swimming in it.