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by Michelle Badash, MS
Pinworms are common parasites that live in the intestine.
A specific, small, white worm causes pinworm infection. A separate species, also causing infection, has been reported in England.
Pinworms are visible to the naked eye. They are about the size of a staple, yellow-white in color, and look like a fine piece of thread, which moves actively.
Pinworms are spread by accidentally eating the eggs of the worm, which can be found on infected clothing, bedding, toys, or in the stool of an infected person.
Pinworms are most active at night, 2-3 hours after bedtime. The female worm comes out through the anus and deposits eggs in the perineal area. This area is between the anus and genitals.
Risk Factors TOP
Pinworms are more common in children 5-14 years old. Other factors that increase your chance of pinworms include:
Symptoms may include:
Symptoms may be worse at night. While the itching caused by pinworms can be very disturbing, pinworms do not otherwise cause serious medical illness. Many people infected with pinworms have no symptoms.
When present, pinworms can frequently be seen in stool or on the skin around the anus. If pinworm infestation is suspected but no worms are seen, then the tape test is often used.
To detect the presence of pinworms, place a piece of clear adhesive tape over the anus, press, and remove. Repeat 2 to 3 times with new tape. Bring adhesive tape samples to the doctor, who will examine them for pinworms. Some laboratories supply special tape or pinworm paddles to use for this test.
The best time to do this test is 2 to 3 hours after bedtime, or before bathing in the early morning.
If treatment is needed, pinworm infections are most commonly treated with prescription medications. Pyrantel pamoate is available as an over-the-counter medication. These medications should be avoided if you are or may become pregnant. Talk to your doctor about therapy if you are or may become pregnant.
You should consult with your doctor to determine the most appropriate treatment. Medication is generally given in 2 or more doses, each separated by 2 weeks. To avoid reinfection, all members of the family should usually be treated.
To help reduce your chance of pinworm infection:
Healthy Children—American Academy of Pediatrics
National Institute of Allergy and Infectious Diseases
The College of Family Physicians of Canada
Enterobiasis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115562/Enterobiasis. Updated February 15, 2010. Accessed September 14, 2016.
Parasites—enterobiasis (also known as pinworm infection). Centers for Disease Control and Prevention website. Available at:
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Updated January 10, 2013. Accessed July 25, 2013.
Last reviewed May 2016 by David Horn, MD
Last Updated: 5/11/2013
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