Young boy uses a dock to jump into Lake Leelanau.

Swimmer’s Itch in Lake Leelanau

You have probably gotten swimmer’s itch at some point in your life, but what is it really, and how can you avoid it? The Lake Leelanau Lake Association (LLLA) is fortunate to partner with some of North America’s top swimmer’s itch researchers. As such, we are privy to the current swimmer’s itch state-of-knowledge and new innovative ways to prevent swimmer’s itch in Lake Leelanau. We invite you to read this week’s blog to learn more!

State-of-Knowledge on Swimmer’s Itch

It was discovered in 1928 that swimmer’s itch is caused by a parasite that cycles between waterfowl in its adult form and snails during its larval form. As it passes between natural hosts, humans can accidentally intercept the microscopic larvae of the parasite, otherwise known as cercariae, causing the uncomfortable symptoms that we know as swimmer’s itch (see the life cycle diagram below).

Swimmer's itch life cycle diagram.

This discovery has set about nearly a century-long quest to control and prevent this common and troublesome malady. Attempts at killing the parasite in bird or snail hosts have been made to break its life cycle. However, these strategies have proven challenging and have unintended negative ecological consequences with limited effectiveness. 

For example, applying copper sulfate to kill the snail hosts kills all aquatic life forms and was shown to be ineffective at stopping swimmer’s itch in research conducted and published on South Lake Leelanau. Furthermore, a recent discovery (2021) has shown that there are more parasite hosts, such as Canada geese, mergansers, and mallards. While diversity is often celebrated as an ecological benefit, when it comes to swimmer’s itch, it makes it harder to control. This discovery has discredited attempts to control swimmer’s itch at the lake-wide level.

Without the ability to control the swimmer’s itch-causing parasite (the avian schistosome cercariae), efforts have now transitioned to prevent swimmer’s itch. Recent discoveries show how the cercariae move through the water. They emerge most abundantly in the morning and travel up to the water’s surface, and then can move around at the surface due to wind and current, often accumulating in shallow water when there are onshore winds. 

This information has helped researchers develop innovative prevention strategies that may be helpful to everyone. Shifting the paradigm from lake-wide control to individual prevention has empowered everyone to swim itch free if proper procedures are employed.

Preventing Swimmer’s Itch in Lake Leelanau

Before enjoying the beautiful waters of Lake Leelanau, please consider the following to prevent swimmer’s itch:

  • Wear a tight-fitting, full-body rash guard—you can find these online! Ocean bathers wear these to prevent jellyfish stings. Larvae typically do not penetrate the fabric. Bonus: less sunscreen is necessary!
  • Swim later in the day! Larvae usually exit snails each morning and will die or be eaten during the day.
  • Avoid lounging in surface waters. Larvae migrate to the surface and can accumulate in shallow water.
  • Avoid onshore winds. Larvae move with the wind and can congregate near windward shores.
  • Towel off after swimming. Some larvae are sticky and can cling to the skin when you exit the water.
  • Swim in deeper water if you are able. Larvae are released from shallow-water snails, so fewer are found in deeper water.
  • Employ a swim baffle.* Baffles show promise in diverting drifting larvae away from swim areas.
  • Skim the swim area surface.* Modified pool leaf rakes show promise in clearing a swim area of the larvae.
  • Try different creams and lotions. Various products claim to repel larvae from entering the skin.
  • Contact your lake association. They may have reporting tools available to avoid areas with recently reported cases. LLLA suggests using this reporting tool to see if others have reported cases nearby and to report your swimmer’s itch case.

*To learn more about the innovative prevention methods local biologists are testing to prevent swimmer's itch in Lake Leelanau and northern Michigan lakes, please visit our Swimmer's Itch page. You can also read local biologists' reports regarding these methods here.

Swimmer’s Itch Symptoms & Treatment

Itching may begin when you are in the water up to a day later and will last for about a week, accompanied by a rash. Please, contact a doctor if inflammation and itching become severe. You can find temporary relief by taking over-the-counter antihistamines, using anti-itch creams/lotions, or soaking in oatmeal or Epsom salts baths.

If you get swimmer’s itch in Lake Leelanau, please report it! You can use to report your cases, view reports before swimming, and learn more about the swimmer's itch.

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