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Swimmer's Itch

What causes swimmers itch?
Swimmers itch is a condition that results when the larval form of a waterfowl parasite (called cercariae) accidentally penetrate into the skin of sensitive individuals. The parasites die, but cause an allergic reaction.

What are the symptoms of swimmers itch?
A reddened spot appears where the parasite attempts to penetrate the skin, much like a mosquito bite. The spot may increase in size and become raised, and is usually accompanied by itching. The symptoms disappear in a few days to a week.

Is swimmers itch a health hazard?
No. The swimmers itch organism is not parasitic to humans and causes no human diseases. No treatment is required for the rash, the rash will go away naturally in a few days, and there are no lasting effects. The itching can be controlled by the same lotions used for mosquito bites and other itching rashes.

Is swimmers itch related to water quality?
No. The presence of swimmers itch is not related to pollution or poor water quality. It is a natural life cycle. Although it has been present in the state for many years, it has never been a significant nuisance problem in most New Hampshire lakes.

Is there any way to prevent the appearance of swimmers itch?
No. Although very few New Hampshire lakes have had reported cases of swimmers itch, there is no guaranteed way to prevent their occurrence. There is, however, a step that will reduce the likelihood of their presence. That step is Don't Feed the Ducks. And don't import or raise ducks or geese along the shore. Ducks are a common adult host of the parasite and the appearance of the parasite is frequently associated with a duck population that is artificially enlarged because of feeding and that congregates near people because of feeding.

How can I avoid swimmers itch?
If the organism is already present in your lake, the following steps can be taken to reduce the chances of encounter.

  • Avoid swimming in the area of reported encounters. The cercariae are weak swimmers and generally remain in the area of infected snails, although the wind may distribute them around smaller lakes.

  • Swim in deeper water. The cercariae are usually found in shallow waters and most easily attach to relatively inactive bodies. Babies sitting along the shore are most vulnerable.

  • Vigorously towel your entire body immediately upon leaving the water. This will brush off any cercariae that may be on the skin and which frequently don't attempt to penetrate the skin until they begin to dry out. If available, taking a quick shower will accomplish the same thing.

  • Use a waterproof sunscreen. This forms a chemical barrier that may discourage the cercariae.

*From the NH Department of Environmental Services