Swimmer’s Itch: Images, Treatment, and More

Swimmer’s itch (cercarial dermatitis) is an itchy rash that can happen after swimming in natural bodies of water. It generally happens in fresh water, but it can occasionally happen in salt water, too. 

The parasite that causes swimmer’s itch doesn’t cause an infection, but the rash can be quite uncomfortable. Swimmer’s itch can last for up to 1 week after a quick dip. Here we’ll explain how it happens and what you can do to treat it.

What causes swimmer’s itch?

Swimmer’s itch is an allergic reaction to a parasite that can live in fresh water. Here’s how it happens:

1. The parasite infects snails that often live in shallow fresh water, like lakes and ponds.

2. The infected snails then release the larval form of the parasite (the “baby” stage, right after the eggs hatch) into the water. 

3. This tiny larva doesn’t cause an infection in humans, but it can burrow under the skin. 

4. Once under the skin, the larva dies and causes an allergic reaction, which leads to itching.

What does swimmer’s itch look like?

Swimmer’s itch causes tiny, itchy spots and bumps where the larvae burrow into the skin. 

In fair skin, the bumps are pink or red. In darker skin, bumps may be violet or skin-colored, making them harder to see. Over the next day or two, the skin bumps can get bigger and even turn into blisters.  

Swimmer’s itch pictures 

Here are some pictures of swimmer’s itch in different skin tones. 

Swimmer’s itch can be more subtle on darker skin.

Swimmer’s itch with crusts on the legs.

What are the symptoms of swimmer’s itch?

The main symptom of swimmer’s itch is a rash, like those shown in the pictures above. But rashes can be hard to identify, especially in the summer, when you spend time outdoors. It can be hard to tell the difference between bug bites, hives, heat rash, and everything else.   

Here are some features that are specific to a swimmer’s itch rash: 

• Onset: The rash usually starts within 1 to 2 hours of swimming. You’ll notice itching or burning before the rash appears.

• Location: The rash usually occurs on areas of skin exposed to lake water. In other words, you won’t get it under a bathing suit.  

• Appearance: Small red, violet, or skin-colored spots or bumps that get bigger over 1 to 2 days. They can turn into blisters, and may crust over if you scratch them. 

• Timeline: Itching lasts about 1 week before it starts to get better. 

• Repeat exposure: Because swimmer’s itch is an allergic reaction, the rash can be more severe every time you get it. 

Is swimmer’s itch dangerous? 

No. Swimmer’s itch can be itchy and uncomfortable, but it isn’t dangerous. If you scratch too much, it can break the skin and lead to a secondary bacterial infection. But this isn’t common. 

Treatment

Swimmer’s itch can be uncomfortable and aggravating. But the good news is that the larvae don’t cause an infection in humans. So you don’t need any specific treatment for the parasite. There are treatments that relieve the symptoms of swimmer’s itch, though. 

Home remedies for swimmer’s itch

Here are some home remedies to try: 

• Ice packs or cool compresses: Cold can soothe itchiness. Bags of frozen vegetables, like peas, are good for this. They can cover larger areas and be reused. To avoid cold injury to the skin, don’t do this for longer than 15 minutes each hour. 

• Oatmeal baths: If the rash covers a large area on your body, an oatmeal bath soak can help ease the itch. 

• Epsom salts: Another bath additive to try is Epsom salts. In general, 2 cups in a full tub of water works well. 

• Baking soda: Mix baking soda with water until you get a paste consistency. Then apply this directly to the rash. 

• Anti-itch lotions: Calamine lotion is another great option. This over-the-counter (OTC) medication made from powdered calamine mineral is cheap and has been used to treat itchy skin for thousands of years.  

• Hydrocortisone: Apply OTC topical steroid cream directly to the rash to help with inflammation and itchiness. Prolonged use of steroid cream can thin out the skin, so don’t use it for longer than a week.  

• Diphenhydramine (Benadryl): Benadryl is a medication you take by mouth, up to every 6 hours. It’s an antihistamine that can help reduce itching. This medication tends to make people sleepy, so it might be better to take it before you go to sleep.

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How to prevent swimmer’s itch

There’s no quick cure for swimmer’s itch, but you can prevent it by following these tips:

• Avoid swimming in places where others report symptoms of swimmer’s itch. If someone swimming in the same waters gets swimmer’s itch, there’s a good chance it could happen to you, too.   

• The larvae are more likely to burrow into skin areas that are exposed to water. So the more covered you are, the better.

• If you develop itching after a swim, avoid going back in the same water. The allergic reaction can worsen with each exposure.

Swimmer’s itch isn’t contagious between people. So you don’t have to worry about catching it from someone who’s affected.

When to get medical attention

Most of the time, you can diagnose and take care of swimmer’s itch at home. 

There’s no specific test to diagnose swimmer’s itch. And you can’t see the larvae that burrow under the skin. A healthcare professional might be able to make the diagnosis based on the rash itself and your symptoms. It can help them if you know when and where your symptoms started. For example, if you’ve been swimming in a natural body of water, especially fresh water, and you developed itchy skin within the hour, that’s useful information to share with them. 

But there’s usually no need to see a medical professional for swimmer’s itch. 

That is, unless your skin rash has become infected. This is possible if you have been itching and scratching your skin a lot. 

Get medical advice if you notice:

• Skin swelling: Instead of seeing small bumps, you may notice a larger area that’s red and swollen.

• Tenderness: Swimmer’s itch generally doesn’t hurt. If your rash becomes infected, the red, swollen area may also start to hurt.

• Drainage: You may notice yellow liquid or pus draining from the swollen areas. This could be a sign your body is trying to rid itself of the infection.

• Streaking: In rare cases, you may notice red streaks from the swollen, tender areas. This can be a sign of a rapidly spreading infection.

• Fever: A fever can sometimes be a later sign of infection. 

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Written by:

Jill L. Jaimes, MD

Jill L. Jaimes, MD, is a board-certified pediatric emergency medicine physician with over 20 years of clinical experience. She received her medical degree from Baylor College of Medicine and completed her residency and fellowship training at Texas Children’s Hospital.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Maria Robinson, MD, MBA

Maria Robinson, MD, MBA, is a board-certified dermatologist and dermatopathologist who has practiced dermatology and dermatopathology for over 10 years across private practice, academic, and telehealth settings. She is a fellow of the American Academy of Dermatology and the American Society of Dermatopathology.

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Images used with permission from VisualDx (www.visualdx.com).