How To: Deal with Sea Lice and Swimmer’s Itch (aka Duck Itch)

Around the world, 2018 has been a hot summer. I predicted early on before the heat wave that 2018 would see a lot of jellyfish, and so it transpired. I also predict that we will see early and more noticeable Sea Lice in swimmers this year, beginning possibly as early as the first week of August (in Ireland).

There two main causes are often mixed up as the symptoms look similar and both are increasingly likely in warmer waters and weather.

Sea Lice

The Jellyfish life-cycle

Sea lice is a generic (and incorrectly used) term. For us in Ireland it is usually not as severe as in warmer waters. In this colloquial context it means tiny jellyfish polyps or copepods or anemones so it is specific to the ocean.

The effects can be worse if you are wearing a wetsuit as the polyps get trapped under it but they can get trapped under swim costumes also.

I’ve haven’t heard of anyone in Ireland who’s had a long-lasting reaction to them, also unlike warmer waters, though I do know it varies by year, and it almost always arrives as a surprise that we’ve forgotten from previous years.  Regular long distance immersion swimmers may find the symptoms can become much more uncomfortable, appearing like pimples, blisters, hives or even severe hives upon hives, simply because there is more time for the exposure to happen.

One easy step to make sure to have a quick fresh water shower (from a bottle if nothing else is available, now the water is warm enough that you can this precaution which I normally warm against in colder waters) immediately after emerging, and one will generally be fine after that. It’s conceivable that a vinegar rinse would be effective also, but generally unnecessary.

There is a lotion called Safe Sea that apparently works well for this and jellyfish stings, but I haven’t seen any experienced (or otherwise) swimmer who’s tried it out.

Swimmer’s Itch, aka Duck Itch, aka Seabather’s Eruption aka Cercarial Dermatitis

Life cycle of the cararial parasite

Duck Schistosome Life Cycle

These terms relate to fresh or brackish waters.  Swimmer’s Itch may be microscopic parasites, i.e. worms, usually from snails, that infect seabirds and mammals, washed into the water as eggs or larvae which, lacking their preferred host, burrow into human skin, causing an allergic reaction, similar to scabies that afflicts many families of young children.

Like scabies, scratching will inflame the area and worsen the symptoms. Unlike scabies the parasites will at least die naturally and infected people are not infectious. It’s also safe to use a swimming pool if you have Swimmer’s Itch.

For worse cases the CDC recommends a number of possible treatments:

  • Use corticosteroid cream
  • Apply cool compresses to the affected areas
  • Bathe in Epsom salts or baking soda
  • Soak in colloidal oatmeal baths
  • Apply baking soda paste to the rash (made by stirring water into baking soda until it reaches a paste-like consistency)
  • Use an anti-itch lotion



5 thoughts on “How To: Deal with Sea Lice and Swimmer’s Itch (aka Duck Itch)

  1. Hello Donal,

    Remember me, taking all of those perfectly staged photos in front of Sandycove Island? Well – I just realised that I totally mucked up the dates in the “black book”… such a shame when I think I wrote 2 months + 2 days, but then forgot that I swum 20 Bridges in September and not October! How do you think that we could fix this?!?!

    Hehe, I guess it is a good problem to have…. I hope you are well – and it was lovely meeting you in Cork last month. Thank you for sharing your stories with me!

    Torgie 🙂


  2. When one experiences duck itch, or other powerfully itchy rashes, a VERY hot shower will produce an endorphin dump and pleasure rush, that will absolutely buckle your knees. Very hot shower is about 47 to 48C, 118F. Hotter than is comfortable for most people, on the brink of scalding . It also provides several hours of relief from itching. You can raise the temp slowly until the rush hits. The effect is stunning. You will want to keep a little patch of tame scabies.


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