Cercarial Dermatitis (Swimmer’s Itch): Symptoms, Causes, Treatment

Cercarial Dermatitis (Swimmer’s Itch): Symptoms, Causes, Treatment

Cercarial dermatitis (Swimmer’s itch) is a skin rash that you can get if you’ve have swum in fresh or salt water that is infested with a certain parasite. It is an allergic reaction, so it is not contagious and will eventually go away on its own. The main symptoms are a rash with reddish pimples and itching or burning. There is no treatment for it, but over-the-counter treatments can relieve the itching.

What is cercarial dermatitis (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 cercarial dermatitis (Swimmer’s itch)?

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 cercarial dermatitis (Swimmer’s itch) 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 cercarial dermatitis (Swimmer’s itch)?

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 cercarial dermatitis (Swimmer’s itch)?

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 cercarial dermatitis (Swimmer’s itch)?

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.

Symptoms and Causes

What causes cercarial dermatitis (Swimmer’s itch)?

A certain parasite larvae, called cercariae, that can be found in fresh (pond or lake water) or salt water (ocean water) causes swimmer’s itch (cercarial dermatitis). The parasite larvae burrow (dig) into your skin and cause an allergic reaction. The parasite larvae cannot survive in the human body, and they die shortly after they burrow into your skin. The rash and itchiness you experience when you have swimmer’s itch is caused by the allergic reaction.

What are the symptoms of cercarial dermatitis (Swimmer’s itch)?

You can develop swimmer’s itch within minutes or days of swimming in infested water.

Symptoms of swimmer’s itch (cercarial dermatitis) include:

  • Tingling, burning or itchy skin.
  • Small, reddish pimples or bumps that form a rash.
  • Small blisters that form a rash.

Is cercarial dermatitis (Swimmer’s itch) contagious?

Swimmer’s itch is not contagious. You cannot spread it to other people or get it from other people.

Diagnosis and Tests

How is cercarial dermatitis (Swimmer’s itch) diagnosed?

There are currently no tests to diagnose swimmer’s itch. It can be difficult to diagnose swimmer’s itch since the rash looks like other skin conditions and rashes, such as poison ivy. It is important to remember that swimmer’s itch is not the only rash that can develop from swimming in fresh water or salt water.

Management and Treatment

How is cercarial dermatitis (Swimmer’s itch) treated?

There is no prescribed or formal treatment for swimmer’s itch. It usually goes away within a week. To get relief from symptoms and itching, you can try the following things at home:

  • Apply a corticosteroid cream to the affected area.
  • Apply a cool compress to the affected area.
  • Use an anti-itch lotion (like calamine) on the affected area.
  • Soak in a colloidal oatmeal bath or an Epsom salts bath.
  • Make a baking soda paste with baking soda and water and apply it to the affected area.

How do I get rid of cercarial dermatitis (Swimmer’s itch)?

Since swimmer’s itch is the result of an allergic reaction, there is nothing you can do to get rid of the rash itself. Your body will eventually heal itself, and the rash will fade away. You can try to relieve the itchiness by using certain at-home remedies like soaking in a colloidal oatmeal bath or using a corticosteroid cream. You can also prevent the rash from getting worse by not scratching it too much or too hard. A lot of scratching can cause an infection.

How long does cercarial dermatitis (Swimmer’s itch) last?

Swimmer’s itch usually goes away on its own within a week, but it could take longer, especially if you have swam in the infested water consecutive times or days. Contact your healthcare provider if your rash lasts longer than two weeks or if there is pus coming out of your blisters.


What can I do to reduce my risk of getting swimmer’s itch (cercarial dermatitis)?

There are a few things you can do to reduce your risk of getting swimmer’s itch, including:

  • Rinse off with clean water after swimming: Rinse your body with clean water right after you’re done swimming. Be sure to dry your skin well with a clean towel.
  • Choose where you swim carefully: Look for signs near the swimming site that could warn you of possible swimmer’s itch contamination and try not to swim in places where swimmer’s itch is a known or common problem.
  • Do not feed birds or animals near where you are swimming: Birds and mammals that live near fresh water or salt water can carry the parasite that causes swimmer’s itch. You don’t want to make them come closer to areas where people are swimming, because they could spread the parasites.
  • Do not swim or wade in or near marshy areas: Snails are more likely to be found in marshy areas, and they can be infected with the parasite that causes swimmer’s itch.
  • If possible, try not to swim or wade in shallow water or by the shoreline: The parasites that cause swimmer’s itch are more likely to be found in shallow water or by the shoreline. If you’re a strong swimmer, consider swimming in deeper water to try to avoid the parasites.

Outlook / Prognosis

What can I expect if I have swimmer’s itch (cercarial dermatitis)?

As its name implies, you can expect lots of itchiness from swimmer’s itch and a rash that has reddish pimples or blisters. The rash from swimmer’s itch will eventually go away, and it could take up to two weeks. Most cases of swimmer’s itch do not require medical attention. But it is important to remember that you could have something else other than swimmer’s itch.

Living With

How do I take care of myself if I have swimmer’s itch (cercarial dermatitis)?

It can be hard to resist, but try not to scratch your swimmer’s itch rash too much. A lot of scratching can cause an infection if your skin breaks open. Use at-home remedies such as a corticosteroid cream, a cold compress or a baking soda paste to ease the itchiness.

When should I see my healthcare provider?

Most of the time, swimmer’s itch does not require medical attention. If you’re experiencing extreme itchiness, your healthcare provider might be able to prescribe you a stronger anti-itch cream.

If your rash lasts longer than two weeks or if you have puss coming out of your blisters, see your healthcare provider.

Additional Common Questions

Can I get swimmer’s itch (cercarial dermatitis) from my swimming pool?

You can’t get swimmer’s itch from pools that are well maintained and treated with chlorine.

Can swimmer’s itch (cercarial dermatitis) spread to other parts of my body?

Swimmer’s itch can only develop on areas of your body that have been in contact with water that is infested with the parasite that causes it. Because of this, it does not spread from the original area of the allergic reaction. However, if you have swam in infested water more than once within the same day or within a couple days, you could have more than one swimmer’s itch rash on your body.

Once water is infested with swimmer’s itch (cercarial dermatitis), will it always be infested?

No. A lot of factors contribute to swimmer’s itch becoming a problem in fresh or salt water since certain birds or mammals and snails all need to be present. Since these factors can change, swimmer’s itch may not permanently be a problem at a swimming place that has been infested with the parasites. However, there is no way to know how long the water may be infested and unsafe. Always look for signage that warns of possible swimmer’s itch contamination before you swim in fresh or salt water.


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