Swimmer's Itch
What is swimmer's itch?
Swimmer's itch, also called cercarial dermatitis, is a
skin rash caused by an
allergic reaction to infection with certain parasites of birds and
mammals. These microscopic parasites
are released from infected snails who swim in fresh and salt water, such as lakes, ponds, and oceans used
for swimming and wading. Infection is found throughout the world.
Swimmer's itch generally occurs during summer months.
What are the signs and symptoms of swimmer's itch?
Within minutes to days after swimming in contaminated
water, you may experience tingling, burning, or itching of the skin.
Small reddish pimples appear
within 12 hours. Pimples may develop into small blisters. Itching may
last up to a week or more, but will gradually go away.
Because
swimmer's itch is caused by an allergic reaction to infection, the more
often you swim or wade in contaminated water, the more likely you are to
develop more serious symptoms. The greater the number of exposures to
contaminated water, the more intense and immediate symptoms of swimmer's
itch will be.
Be aware
that there are other causes of rash that may occur after swimming in
fresh and salt water.
Do I need to see my health care provider for treatment?
No. Most cases do not require medical attention.
If you have a rash, you may try the following for relief:
- corticosteroid cream
- cool compresses
- bath with baking soda
- baking soda paste to the rash
- anti-itch lotion
- Calamine* lotion
- colloidal oatmeal baths, such as Aveeno*
Try not
to scratch. Scratching may cause the rash to become infected. If itching
is severe, your health care provider may prescribe lotion or creams to
lessen your symptoms.
How does water
become infested with the parasite?
The adult parasite lives in the
blood of infected animals such as ducks, geese, gulls,
swans, as well as certain aquatic mammals such as muskrats and beavers.
The parasites produce eggs that are passed in the feces of the
infected birds or mammals.
If the
eggs land in the water, the water becomes contaminated. 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 and undergo further development. Infected snails release a different type
of larvae (cercariae, hence the name cercarial dermatitis) into the water. This
larval form then searches for a suitable host (bird, muskrat) so they
can start the lifecycle over again. Although humans are not a suitable
host, the larvae burrow into the skin of swimmers, which may cause an
allergic reaction/rash. The larvae cannot develop inside a human and
they soon die.
Can swimmer's itch be spread from person-to-person?
No.
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 swimming along shallow water by the shoreline. Children are most
often affected because they swim, wade, and play in the shallow water
more than adults. Also, they do not towel dry themselves when leaving
the water.
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