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Thurston County, Washington

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swimmer's itch at black lake image

OLYMPIA – Thurston County Public Health and Social Services advises members of the community that the parasite that causes swimmer’s itch appears to be present in Black Lake. Swimmers at any freshwater lake need to be aware that this parasite may be present and there are ways to avoid being infected by it.

Swimmer’s itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals. These parasites are released from infected snails into fresh and saltwater (such as lakes, ponds, and oceans). If the parasite comes into contact with a swimmer, it burrows into the skin causing an allergic reaction and rash.

Swimmer’s itch is found throughout the world and is more frequent during summer months. The parasite does not have long-term effects for those who encounter it. Symptoms may include tingling, burning, or itching of the skin.

Follow these steps to reduce your likelihood of getting swimmer’s itch:

  • Choose not to swim in areas where swimmer’s itch is a known problem or where signs have been posted warning of unsafe water.
  • Choose not to swim near or wade in marshy areas where snails are commonly found.
  • Towel dry or shower immediately after leaving the water.
  • Apply water-proof sunscreen to your body before entering the water to both protect you from the sun and reduce the ability of the parasite to attach to the skin.
  • Do not attract birds (e.g., by feeding them) to areas where people are swimming.  


Public Health and Social Services
Closures, Health

Questions and inquiries regarding News Release content should be directed to the Thurston County Public Information Officer:  

Meghan Porter

Anna Rhoads