by EBSCO Medical Review Board
(Cercarial Dermatitis; Duck Fleas; Duck Itch; Duckworms; Sea Lice; Clam Digger's Itch)


Swimmer’s itch is a skin rash that appears on parts of the body that have been in natural bodies of water that contain certain parasites. It is more common in warm freshwater (lakes and ponds), but it can also occur in salt water.


This problem is caused by an allergic reaction to certain parasites. The parasite enters the water through the waste of infected birds and snails. It can burrow under the skin and cause a reaction when it comes in contact with a person's skin.

Risk Factors

This problem is more common in children. This is because they spend more time in shallow water.

Other things that may raise the risk are:

  • Having swimmer’s itch in the past
  • Swimming or wading in warm fresh or salt water
  • Swimming or wading in warm shallow water near the shoreline
  • Swimming in locations with onshore winds
  • Swimming in areas with a lot of birds
  • Spending long periods of time in the water


Symptoms can start quickly. Problems may be:

  • Itching
  • A feeling of burning or tingling
  • Small red bumps, blisters, or pimples
Blistering Skin from Swimmer's Itch
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The doctor will ask about your symptoms and health history. You will be asked about any recent time spent in natural bodies of water. A physical exam will be done. It will focus on your skin. This is enough to make the diagnosis.


The rash will go away on its own within a few days or up to one week.

Supportive care can help ease symptoms. Choices are:

  • Soothing baths and cool compresses
  • Over the counter cortisone creams and anti-itch medicines
  • Oral antihistamines

People who are not helped by these methods may need prescription medicines.


The risk of this problem may be lowered by:

  • Not swimming in areas where swimmer's itch is a known problem
  • Not swimming near or wading in marshy areas where snails are found
  • Towel drying or showering after leaving the water


American Academy of Dermatology 

Centers for Disease Control and Prevention 


Canadian Dermatology Association 

Public Health Agency of Canada  https://www. 


Colley DG, Bustinduy AL, et al. Human schistosomiasis. Lancet. 2014 Jun 28;383(9936):2253-2264.

Parasites—Cercarial dermatitis (also known as swimmer’s itch). Centers for Disease Control and Prevention website. Available at: Accessed March 19, 2021.

Schistosomiasis. EBSCO DynaMed website. Available at: Accessed March 19, 2021.

Swimmer’s itch. American Osteopathic College of Dermatology website. Available at: Accessed March 19, 2021.

Swimmer’s itch. DermNet New Zealand website. Available at: Accessed March 19, 2021.

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