What is swimmer’s itch?
Swimmer’s itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to certain parasites that infect some birds and mammals. These microscopic parasites are released from infected snails into fresh and salt water, such as lakes, ponds and oceans.
While the parasite’s preferred host is the specific bird or mammal, if the parasite comes into contact with a swimmer, it burrows into the skin sometimes causing an allergic reaction and rash.
How does water become infested with the parasite?
The adult parasite lives in the blood of infected animals such as ducks, geese, gulls, swans and certain aquatic mammals such as muskrats and beavers. The parasites produce eggs that are passed in the feces of infected birds or mammals.
If the eggs land in or are washed into the water, the eggs hatch, releasing small, free-swimming larvae. These larvae swim in the water in search of a certain species of aquatic snail.
If the larvae find one of these snails, they infect the snail, multiply and undergo further development. Infected snails release a different type of larvae (or cercariae, hence the name cercarial dermatitis) into the water. This larval form then swims about searching for a suitable host to continue the lifecycle. Humans are not suitable hosts and if larvae burrow into the swimmer’s skin they soon die.
What are the signs and symptoms of swimmer’s itch?
Symptoms of swimmer’s itch may include:
- tingling, burning, or itching of the skin
- small reddish pimples
- small blisters
Within minutes to days after swimming in infested water, you may experience tingling, burning, or itching of the skin. Small reddish pimples appear within twelve hours. Pimples may develop into small blisters. Scratching the areas may result in secondary bacterial infections. Itching may last up to a week or more, but will gradually go away.
Do I need to see my health care provider for treatment?
Most cases of swimmer’s itch do not require medical attention. If you have a rash, you may try the following for relief:
- Use corticosteroid cream
- Apply cool compresses to the affected areas
- Bathe in Epson salts or baking soda
- Soak in colloidal oatmeal baths or use over-the-counter moisturizing creams or ointments
- Apply baking soda paste to the rash (made by stirring water into baking soda until it reaches a paste-like consistency)
- Use an over-the-counter anti-itch lotion, as directed
Though difficult, try not to scratch. Scratching may cause the rash to become infected. If itching is severe, your health care provider may suggest prescription-strength lotions or creams to lessen your symptoms.
Can swimmer’s itch be spread from person-to-person?
Swimmer’s itch is not contagious and cannot be spread from one person to another.
Who is at risk for swimmer’s itch?
Anyone who swims or wades in infested water may be at risk. Larvae are more likely to be present in weedy areas and shallow water by the shoreline. Children are most often affected because they tend to swim, wade and play in the shallow water more than adults.
Once an outbreak of swimmer’s itch has occurred in water, will the water always be unsafe?
No. Many factors must be present for swimmer’s itch to become a problem in water. Since these factors change, swimmer’s itch will not always be a problem. However, there is no way to know how long water may be unsafe. Larvae generally survive for 24 hours once they are released from the snail. However, an infected snail will continue to produce cercariae throughout the remainder of its life. For future snails to become infected, migratory birds or mammals in the area must also be infected so the lifecycle can continue.
Is it safe to swim in my swimming pool?
Yes. As long as your swimming pool is well maintained and chlorinated, there is no risk of swimmer’s itch. The appropriate snails must be present in order for swimmer’s itch to occur.
What can be done to reduce the risk of swimmer’s itch?
To reduce the likelihood of developing swimmer’s itch:
- Towel dry or shower immediately after leaving the water.
- Do not attract birds (e.g., by feeding them) to areas where people are swimming.
- Avoid swimming in areas where swimmer’s itch has been known to be a problem..
- Avoid swimming or wading near marshy areas where host snails are commonly found.
This Fact Sheet was adapted from the Centers for Disease Control and Prevention. For further information on protecting yourself from recreational water illnesses, please visit http://www.cdc.gov/healthyswimming/index.htm
