Swimmer's itch: how can I protect myself when bathing in open water?

It's a great way to cool off, but be aware that during the summer many lakes contain microscopic parasites that can cause an itchy rash. This health tip tells you how to treat and prevent this kind of rash.
07.08.2024 | 2 minutes reading time
Author:
Content-Team SWICA
It's peak season for open water swimming, and Switzerland's many lakes offer the perfect way to cool down on hot summer days. But they also provide a habitat for cercariae, the tiny larvae of a type of parasitic flatworm that lives in the gut of aquatic birds. The flatworms' eggs get into the water via the birds' droppings, and once there they hatch into larvae that are able to move about freely in the water.
These larvae are harmless to humans as long as the water temperature stays below 20 °C, when they prefer aquatic snails as hosts. Should the temperature rise above that level, however, they set off in search of their final host – an aquatic bird. If they come into contact with a human in the water, they are unable to distinguish between their skin and that of a bird and so start to burrow into it. As human skin is significantly thicker, however, the larvae get stuck. At this point, the immune system is triggered and starts working to repel the invaders. This immune response can produce an extremely itchy rash.
Although the itching can be very irritating, particularly when it affects a large area, the larvae pose no danger to humans. You can treat the itchy pustules in a similar way to insect bites. Lotions containing polidocanol (a local anaesthetic), gels for treating mosquito bites and antihistamines can all help reduce the unpleasant burning sensation. Try not to scratch too hard if possible, as you could damage the skin and make it more vulnerable to bacteria, which can lead to infections. The rash usually clears up within 14 days. You should seek medical advice if the pustules get worse or don't heal by themselves.

How can you protect yourself against swimmer's itch?

  • One surefire way is to only swim in flowing water, where the larvae are unable to survive. You're also safe in salt water.
  • Look for a bathing spot where there aren't lots of ducks, swans or geese in the water, as these are where the concentration of larvae is highest.
  • Shower and dry yourself off thoroughly after spending time in the water.
  • Change your swimwear afterwards.
    ​

As our summers get hotter and longer, more and more bodies of water are hitting the critical temperature of 20 °C. They are also reaching this temperature sooner, and the period during which the water is warm enough for the larvae is getting longer, which is why cases of swimmer's itch are on the rise.

Skin check: quick, professional help with skin conditions

Whether you have a rash, a fungal infection, or itchy or inflamed skin, you can have your condition assessed quickly and easily by a specialist. santé24 offers SWICA customers free, expert dermatological advice and, whenever possible, a recommended course of treatment. SWICA also works with the OnlineDoctor platform, which SWICA customers can use to ask medical experts to assess their skin problems.

For SWICA customers: santé24 and Benecura

In the event of further health-related questions, SWICA customers can contact the santé24 online practice free of charge on +41 44 404 86 86. A telemedicine practice licence allows santé24 physicians to provide additional medical services in cases that are suited to a telemedicine approach.

SWICA customers can also use the Benecura medical app to carry out a digital SymptomCheck and receive recommendations about what to do next. During a subsequent phone call with santé24, customers can decide for themselves whether to release their information from SymptomCheck to santé24.

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