HealthLink BC File #52, May 2011
- What is swimmer's itch?
- Where are these parasites found?
- How can you avoid swimmer's itch?
- What are the symptoms of swimmer's itch?
- How long do the symptoms last?
- How do you treat swimmer's itch?
- Is swimmer's itch dangerous?
What is swimmer's itch?
Swimmer's itch is a temporary, itchy rash caused by small worm-like parasites called schistosomes (Shiss-toe-soams). These little worms are found in many lakes and ponds in British Columbia, usually in the warm summer months.
Schistosomes spend their life cycle as parasites in the bodies of water snails and in the blood stream of aquatic mammals, ducks or other waterfowl. Schistosome larvae leave their snail host and swim around near the surface of the water, intending to come into contact with birds and certain mammal hosts. Larvae sometimes mistakenly get on to the skin of people swimming or wading, instead of aquatic mammals or waterfowl.
After a person leaves the water, these larvae start to burrow under the skin. However, these larvae can not survive in humans and die almost immediately after they burrow into the skin. It is the allergic reaction to these tiny larvae under the skin that causes the itchy rash or swimmer's itch.
Where are these parasites found?
On-shore winds tend to push the tiny larvae to the edges of lakes where these float near the surface. Although less common, cases of swimmer's itch have been reported at certain coastal beaches in British Columbia � a result of a species of snail from the Atlantic coast.
Young children who wade and splash in shallow areas of lakes and ponds may be at higher risk due to the following factors:
- They are constantly getting wet, without thoroughly drying off.
- They usually play by the shore where these parasites tend to concentrate.
- Their young, tender skin is more sensitive.
How can you avoid swimmer's itch?
There is no sure way to avoid swimmer's itch entirely, unless you avoid lakes and ponds. Before going into any lake, find information about the lake by speaking with other people there and with local health officials or parks representatives. Some lakes may be posted as having a swimmer's itch problem. Check for warning signs at public beaches and areas.
If you are not sure about a lake, avoid areas with lots of weed growth. There may be more snails around plants, and there may also be more larvae.
There tend to be more larvae near the shore. If there is a pier or wharf to enter the water, doing so may reduce your risk of exposure. However, make sure the pier has been approved for swimming. Do not dive into unknown waters.
Applying waterproof sunscreen before bathing may help reduce the number of larvae from penetrating the skin.
Most importantly, dry yourself quickly with a dry towel as soon as you come out of the water. Ideally, you should have a shower and then dry yourself with a towel right away. However, showering will not remove any larvae that have already penetrated into the skin.
What are the symptoms of swimmer's itch?
The degree of symptoms will depend on how many larvae get on to your skin, and how sensitive you are to them. Symptoms also tend to get worse with repeated exposures.
Swimmer's itch ranges from just a mild irritation to a very severe, itchy red rash. This may become badly infected from too much scratching.
When a person starts to dry off and the larvae start to burrow into the skin, a tingling feeling may begin almost right away. Small, pin-point sized red spots will appear, which grow into larger red rashes within several hours. As these red spots grow, the tingling feeling becomes a strong itch, which feels like a nettle's sting or an insect bite.
How long do the symptoms last?
The itching feeling will gradually get worse, and it may last 2 to 5 days or as long as 2 weeks before fading away slowly.
Too much scratching can cause severe pain and swelling or other skin infections.
Repeat infections are usually worse because people become more sensitive to the larvae and develop stronger allergic responses each time.
The rash can not be spread from person to person.
How do you treat swimmer's itch?
There are a number of steps you can take, which may reduce some of the itchiness. Check with your doctor or pharmacist about treatment. Commonly recommended treatments and advice include:
- Avoid scratching.
- Apply plain calamine lotion.
- Take antihistamines, especially at bedtime. These are not recommended for children under 6 years of age.
- Take shallow, lukewarm baths with three tablespoons of baking soda in the water.
- Take colloidal oatmeal baths.
- Apply cool compresses.
Is swimmer's itch dangerous?
The rash and itch can be very irritating especially for young children, but there should not be any serious danger. However, if a skin infection occurs from too much scratching, you should see your doctor.
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