Swimmer's itch is a rash caused by an allergic reaction to the larvae of certain parasites. The parasites can get under your skin when you swim in freshwater (such as lakes and ponds) and sometimes salt water. But you can't get swimmer's itch from swimming pools that are treated with chlorine.
The tiny parasites infect birds or mammals and lay eggs. Bird and mammal droppings that contain the eggs get into lakes and ponds. The eggs hatch into larvae, which then infect snails. The snails in turn release the larvae into the water, where the larvae look for a host. If they come in contact with people, the parasites can burrow under the skin. This causes an allergic reaction and a rash.
But the larvae can't survive in humans, so the parasites die. As a result, the rash usually goes away on its own and doesn't need treatment. The rash can't be spread from person to person.
What are the symptoms?
Symptoms of swimmer's itch include:
A rash that usually goes away in about a week.
An itching or burning feeling on your skin.
Pimples that show up minutes or even days after you were in the water. The pimples may later turn into blisters.
How severe the rash is may vary for people exposed to the same parasites.
How is swimmer's itch diagnosed?
A doctor can diagnose swimmer's itch by looking at your skin and asking if you've been swimming in ponds or lakes.
How is it treated?
In most cases, swimmer's itch goes away on its own, so you don't need to see a doctor.
To treat the itching at home, you can:
Put cool wet cloths (compresses) on your skin.
Use anti-itch creams that you can buy without a prescription in a grocery store or drugstore.
Put calamine lotion on your skin.
Add a handful of oatmeal (ground to a powder) to your bath. Or you can try an oatmeal bath product, such as Aveeno.
Try not to scratch the rash. This could lead to an infection.
Call your doctor if you still have a rash after 1 week or if you have signs of infection, such as:
Increased pain, swelling, warmth, or redness.
Red streaks leading from the area.
Pus draining from the area.
Can you prevent swimmer's itch?
To lower your chance of getting swimmer's itch:
Don't go near lakes or ponds that are known to have outbreaks of swimmer's itch.
Shower or dry yourself off with a towel as soon as you get out of a lake or pond.
Centers for Disease Control and Prevention (2011). Parasitesâ€”cercarial dermatitis (also known as swimmer's itch). Available online: http://www.cdc.gov/parasites/swimmersitch/faqs.html.
ByHealthwise StaffPrimary Medical ReviewerWilliam H. Blahd, Jr., MD, FACEP - Emergency MedicineAdam Husney, MD - Family MedicineMartin J. Gabica, MD - Family MedicineElizabeth T. Russo, MD - Internal MedicineSpecialist Medical ReviewerH. Michael O'Connor, MD, MMEd, FRCPC - Emergency Medicine