The condition is called swimmer's itch and is caused by tiny parasites - cercariae. The parasites, which are invisible to the naked eye, develop in freshwater snails and mainly parasitize seabirds. But they can also misbehave and attack a bather by penetrating a few millimetres into the skin.
The traces left behind are itchy, red rashes that resemble mosquito bites.
"It causes an allergic reaction when these parasites crawl into the skin. It sounds horrible, but they die when they enter the skin," says Therése Rödjemark-Andersson, nurse and acting director of operations at 1177 Region Stockholm.
Accelerating in the heat
The parasites are more noticeable when it's really hot. Cercariae are excreted more quickly from the snails at higher temperatures, that is, when the bathing areas are most visited.
Although swimmer's itch can itch like hell, it is generally harmless, points out Therése Rödjemark-Andersson.
There is no need to worry. It is very rare for anyone to get sick from the parasites.
Can be countered
It is more common for children to be affected, as the snails are mainly found in shallow water. But Therése Rödjemark-Andersson does not think that families with children need to forgo swimming trips just to be on the safe side. The risks can be countered.
The important thing is to shower, either directly at the beach or when you get home, to dry yourself after swimming and to change into your swimsuit. If you still suffer from itching, you can buy over-the-counter preparations such as cortisone cream or cooling balm at the pharmacy. A wet, cold towel can also provide relief.
She also urges those who suffer from swimmer's itch to report it to the municipality, which can issue a broad warning and possibly close the bathing area temporarily.
The parasites that cause swimmer's itch are mainly found in fresh or brackish water.
It is more common for children to get swimmer's itch, because children often bathe for longer periods of time and in shallow, warm water where there may be more parasites.
The itching may occur after a few minutes or may last for a few days.
A few people may suffer from a more serious allergic reaction, but this is rare. You can get an infection if you scratch the rash, and you may also get a fever.
The itching usually goes away on its own. The vast majority of people who experience the problem do not need to seek medical attention.
Swimmer's itch is not contagious between people.
