(Cercarial Dermatitis; Duck Fleas; Duck Itch; Duckworms; Sea Lice; Clam Digger's Itch)
by Michael Jubinville, MPH
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.
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.
Swimmer’s itch is more common after:
Swimmer’s itch is also more common in children since they tend to stay in shallow water.
Symptoms can occur quickly. In most cases, you will notice skin irritation before the rash appears. Symptoms can include:
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.
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:
A severe rash may require prescription strength medication.
To help reduce your chances of getting swimmer’s itch:
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: https://www.cdc.gov/parasites/swimmersitch/index.html. Updated January 10, 2012. Accessed December 14, 2017.
Schistosomiasis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T901358/Schistosomiasis . Updated August 14, 2017. Accessed December 14, 2017.
Swimmer’s itch. American Osteopathic College of Dermatology website. Available at:
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Accessed December 14, 2017.
Swimmer’s itch. DermNet New Zealand website. Available at: https://www.dermnetnz.org/topics/swimmers-itch. 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 November 2018 by EBSCO Medical Review Board Marcie L. Sidman, MD
Last Updated: 12/14/2017
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