Pinworms are common parasites that live in the intestine.

The Intestines

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A certain type of white worm causes the infection.

Pinworms can be seen. They look like a piece of thread and are about the size of a staple. They're spread by accidentally eating the eggs of the worm. They can be found on clothing, bedding, toys, or in the stool of someone who has them.

Pinworms are most active at night, 2-3 hours after bedtime. The female worm comes out through the anus and deposits eggs in the perineum area. This area is between the anus and genitals.

Risk Factors

Pinworms are more common in children aged 5-14 years old. Your chances of pinworms are higher for:

  • Contact with a person who has them—usually another child or family member
  • Contact with clothing, bedding, or objects that have pinworms on them
  • Regular exposure to schools, daycare centers, and other places where pinworms are found


Many people with pinworms don't have problems. In those that have them, they may cause:

  • Itching and scratching in the anal area—gets worse at night
  • Problems with sleep


Pinworms can be seen in stool or on the skin around the anus. If pinworms are suspected, but can't be seen, then you may have a tape test.

Place a piece of clear tape over the anus, press, and remove. Repeat it 2 to 3 times with new tape. Bring the tape samples to the doctor. They will check them for pinworms. Some labs 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. It can also be done before bathing in the early morning.


If needed, pinworms are treated with medicines. They're given in 2 or more doses, each separated by 2 weeks. To avoid reinfection, all members of the family should be treated.


To help lower your chances of a pinworm infection:

  • Wash hands thoroughly after using the toilet, changing diapers, and before cooking or eating.
  • Change and wash underwear daily.
  • Bathe shortly after waking up to reduce egg contamination.
  • Discourage nail biting and scratching anal areas.

Healthy Children—American Academy of Pediatrics

National Institute of Allergy and Infectious Diseases


Health Canada

The College of Family Physicians of Canada


Enterobiasis. EBSCO DynaMed Plus website. Available at: Updated August 16, 2017. Accessed August 15, 2018.

Parasites—enterobiasis (also known as pinworm infection). Centers for Disease Control and Prevention website. Available at: Updated January 10, 2013. Accessed August 15, 2018.

Pinworm infestation. Merck Manual Professional Version website. Available at: Updated February 2017. Accessed August 15, 2018.

Last reviewed May 2018 by EBSCO Medical Review Board Daus Mahnke, MD  Last Updated: 8/15/2018