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What is Swimmer’s Itch – and How Can I Avoid It?

written by
Linda McDonagh

Have you ever had floods of families report that their children have suddenly developed itchy pimples or blisters all over themselves shortly after a summer’s day swim?

This may have been what’s known as ‘Swimmer’s Itch’.

What is Swimmer’s Itch?

Swimmer’s itch is a rash caused by an allergic reaction to specific kinds of parasitic larvae that spawn within the freshwater body that’s being swum in. It isn’t contagious and it usually lasts only a week or so. It often has the below symptoms:

  • A tingling sensation after exiting the water and allowing the freshwater to evaporate off
  • Small, red pimples (that later can develop into blisters) appearing anywhere from minutes to a day after exposure
  • These bumps either itching or burning for up to a week

In the Midwest, these rashes usually develop in the first weeks of the summer when water initially warms up, and outbreaks themselves generally last no longer than four weeks. Depending on your location and its seasonality, this may differ.

Note – not every rash developed after swimming in freshwater is swimmer’s itch, and while you usually don’t need to visit a doctor for medical care for swimmer’s itch, you should monitor symptoms for worsening or ongoing effects, such as:

  • Increased pain, swelling, warmth, or redness.
  • Red streaks leading from the affected area
  • Pus
  • Fever

    User:Cornellier, CC BY-SA 3.0, via Wikimedia Commons

What Causes Swimmer’s Itch – Parasites?

Geese sitting along a lake structure - geese can be a source of the parasite that causes Swimmer's Itch

Those larvae parasites? They come from adult versions that infect animals (such as ducks, geese, seagulls, swans and more) and produce eggs that are passed along in their host’s droppings.

When those feces either land or wash into a waterbody, the eggs within hatch, resulting in microscopic larvae that swim through the water. These swimming larvae then search out and infect specific species of aquatic snails.

Once infected, these larvae undergo some development and are released as slightly different microscopic larvae which then search out a new host. Ideally, this would be something like a bird or a muskrat, but these larvae can attach to humans, burrowing into their skin and causing a reaction.

Unfortunately for the larvae, they can’t develop inside humans and shortly die. Fortunately for humans, this means that they usually don’t need any treatment and the rash dissipates on its own.

Can You Prevent Swimmer’s Itch in Ponds or Lakes?

Swimmers in a lake

Due to the spread of swimmer’s itch being so closely related to aquatic life, it can be difficult to prevent these parasites from spreading without disrupting the environmental balance. You also just can’t keep birds and other animals from defecating in your lake or pond.

For everyday swimmers, you can suggest they try the below to avoid or at least lower their chances of developing swimmer’s itch:

  • Towel off after swimming or wading in water (rather than simply allowing it to evaporate), this can help crush and kill the parasites before they burrow into your skin
  • Follow this by quickly showering and rinsing off skin
  • Swim in deeper waters away from the shore
  • If you notice snails on docks, rocks, or vegetation – avoid swimming in that area
  • Don’t feed birds and be mindful of not sweeping their wastes from docks into the water
  • Upon receiving reports of swimmer’s itch, post signage warning other swimmers
  • Suggest those who have it to confirm with their doctor – while swimmer’s itch is common, there are other rashes that can be caused by bacteria within waters

Find a full list of suggestions, best practices, and a FAQ on the CDC’s website. We also recommend checking out information from your state’s DNR, such as Wisconsin’s or Minnesota’s.

Improving Water Quality, Improving Communities

If you’re working to ensure a safe, uninterrupted, fun-filled summer for your community, consider contacting our team for a consultation and a custom solution fitted to your unique needs.

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