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Swimmer’s Itch

(Cercarial Dermatitis; Duck Fleas; Duck Itch; Duckworms; Sea Lice; Clam Digger's Itch)


Swimmer’s itch is a skin rash that appears after you have been swimming or wading in natural bodies of water. It is more common in warm freshwater (lakes and ponds), but it can also occur in salt water.

Causes    TOP

Swimmer’s itch is an allergic reaction to a specific parasite. The parasite enters the water through the waste of infected birds and snails. If the parasite comes in contact with your skin, it can burrow under the skin and cause a reaction.

Risk Factors    TOP

Swimmer’s itch is more common after:

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

Swimmer’s itch is also more common in children since they tend to stay in shallow water.

Symptoms    TOP

Symptoms can occur quickly. In most cases, you will notice skin irritation before the rash appears. Symptoms can include:

  • Itching
  • A sensation of burning or tingling
  • Small red bumps, blisters, or pimples

Blistering Skin from Swimmer's Itch

Copyright © Nucleus Medical Media, Inc.

Diagnosis    TOP

There is no skin or blood test to diagnose swimmer’s itch. The doctor will base the diagnosis on information about recent activities and the appearance of the rash.

Treatment    TOP

The rash will go away on its own within a few days or up to one week without medical treatment.

Scratching can cause further damage to the skin and increase the risk of infection. Itching may be relieved with:

  • Soothing baths and cool compresses
  • Over-the-counter cortisone creams and anti-itch medications
  • Oral antihistamines—for more severe itching

A severe rash may require prescription strength medication.

Prevention    TOP

To help reduce your chances of getting swimmer’s itch:

  • Apply a barrier lotion with broad-spectrum sunscreen product before going in the water.
  • Avoid swimming or wading in known contaminated waters. Also try and avoid areas of water with a lot of birds or marshy areas where there are snails.
  • Rub your (and your child’s) skin with a towel after coming out of the water.
  • Wash bathing suits, towels, and clothing that was worn to the beach.


American Academy of Dermatology
Centers for Disease Control and Prevention


Canadian Dermatology Association
Public Health Agency of Canada


Parasites—Cercarial dermatitis (known as swimmer’s itch). Centers for Disease Control and Prevention website. Available at: Updated January 10, 2012. Accessed December 14, 2017.
Schistosomiasis. EBSCO DynaMed Plus website. Available at: Updated August 14, 2017. Accessed December 14, 2017.
Swimmer’s itch. American Osteopathic College of Dermatology website. Available at:
...(Click grey area to select URL)
Accessed December 14, 2017.
Swimmer’s itch. DermNet New Zealand website. Available at: Accessed December 14, 2017.
Verbrugge LM, Rainey JJ, Reimink RL, Blankespoor HD. Prospective study of swimmer’s itch incidence and severity. J Parasitol. 2004;90(4):697-704.
Last reviewed December 2017 by EBSCO Medical Review Board Marcie L. Sidman, MD
Last Updated: 12/14/2017

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This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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