Swimmer’s itch, also called cercarial dermatitis, is a
skin rash caused by an allergic reaction to infection
with a parasite.
How is swimmer’s itch transmitted?
The microscopic parasites (which live in birds and
mammals) can infect snails. These parasites, in the
form of larvae, are released from infected snails to
swim in fresh and salt water, such as lakes, ponds,
and oceans used for swimming and wading.
Humans get swimmer’s itch when the larvae (cercarial) burrow into the skin. The larvae cannot
develop inside a human and they soon die.
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.
most often affected because they swim, wade, and
play in shallow water more than adults. Also, they
do not towel dry themselves when leaving the water.
What are the signs and symptoms of
Within minutes to days after swimming in
contaminated water, a person may experience
tingling, burning, or itching of the skin.
reddish pimples appear with 12 hours.
develop into small blisters.
Itching may last up to a
week or more, but will gradually go away.
What is the treatment for swimmer’s itch?
The following may give relief:
Bath with baking soda
Colloidal oatmeal baths, such as Aveeno
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.
Can you get swimmer’s itch more than once?
Yes. 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.
Can swimmer’s itch be spread from person-to-person?
Once an outbreak of swimmer’s itch has
occurred in water, will the water always be
No. Many factors must be present for swimmer’s
itch to become a problem in water. Since these
factors change (sometimes within a swim season), swimmer’s itch will not always be a problem.
However, there is no way to know how long water
may be unsafe.
What can be done to reduce the risk of
Avoid swimming in areas where swimmer’s itch
is a known problem or where signs have been
posted warning of unsafe water.
Avoid swimming near or wading in marshy
areas where snails are commonly found.
Towel dry or shower immediately after leaving
This is important since the larvae do
not penetrate the skin until the water evaporates
(the towel should not be used again until it has
Encourage health officials to post signs on
shorelines where swimmer’s itch is a current
Do not attract birds by feeding them in areas
where people are swimming.
Is my swimming pool safe to swim in?
Yes. As long as your swimming pool is well maintained
and chlorinated, there is no risk of
Are there other causes of rash that may occur
after swimming in fresh and salt water?
Where can I get more information?
Contact your physician or the Southern Nevada Health District, Office of Epidemiology at (702) 759-1300.
This fact sheet, which is based on information from the Centers
for Disease Control, is for information only and is not meant to
be used for self-diagnosis or as a substitute for consultation with
a health care provider. If you have any questions about the
disease described above or think that you may have a parasitic
infection, consult a health care provider.