Division of Public Health Services  Disease Handbook for Childcare Providers 
Bureau of Infectious Disease Control   REVISED –January 2018 
SWIMMER’S ITCH (Cercarial Dermatitis) 
 
Swimmer’s itch (Cercarial Dermatitis) is caused 
by human contact with a parasite that normally is 
found in some species of birds or small animals.  
The adult stage of the parasite lives in the 
animals’ intestines and is shed into the water with 
excreted feces.  Snails feed off the waste and 
release the young parasite (called cercaria) into 
the water.  When this parasite burrows into a 
person’s skin it causes an allergic, itchy rash.  The 
parasite is commonly found at  the water’s surface 
and near the shore. 
 
Who gets this disease? 
Anyone who swims in water where this parasite 
lives is susceptible.  The parasite may live in both 
fresh and salt water. 
 
How is it spread? 
Most commonly, individuals get the infection by 
swimming or wading in infested water and then 
allowing water to evaporate off the skin rather 
than drying the skin with a towel.  The parasite 
(cercaria) will borrow underneath the person’s 
skin.  Because these parasites cannot develop 
inside a human, they so on die.  The infection is 
not spread from person-to-person. 
 
What are the symptoms? 
The symptoms include an initial prickling 
sensation after leaving the water shortly followed 
by an itchy rash, which reaches maximum 
intensity in 2 to 3 days and can persis t for a week.  
Scratching the area may result in secondary 
bacterial infections.  Repeated exposure increases 
a person’s sensitivity to the parasite, possibly 
resulting in more severe symptoms. 
What is the treatment? 
It is best to check with a physician f or treatment.  
Sometimes medication is given to ease the itching 
and allergic reaction.  If secondary infection 
develops, antibiotic treatment may be indicated. 
 
How can Swimmer’s Itch be prevented? 
1. Avoid swimming in known infested 
waters.  Swim in deeper water.  The 
parasite is usually found in shallow 
waters.  Babies sitting along the shore are 
most vulnerable. 
2. Vigorously towel your entire body 
immediately upon leaving the water.  This 
will help brush off any cercaria that may 
be on the skin, also rinsing  off with a 
quick shower as soon as you leave the 
water may be helpful. 
3. Use a waterproof sunscreen.  This forms a 
chemical barrier that may prevent the 
parasite from sticking to the body. 
 
Who should be excluded? 
There is no need to exclude someone from a 
facility since Swimmer’s Itch is not spread from 
person-to-person. 
 
Reportable? 
No, Swimmer’s Itch is not reportable by New 
Hampshire law to the Division of Public Health 
Services, Bureau of Infectious Disease Control.  
However, public health professionals are available 
for consultation at (603)-271-4496. 
 
For questions in sampling public swimming areas, 
please contact the NH Department of 
Environmental Services, Public Beach Sampling 
Program at (603) 271-0698.