Pinworm infection is caused by a specific type of small, thin, white roundworm. They look like a piece of thread and are about the size of a staple.

The infection spreads when a person eats the worm's eggs. This can happen from contact with the stool of an infected person. It can also happen by touching clothing, bedding, food, or other items that have them.

Risk Factors

Pinworm infection is more common in children under 14 years of age. Other things that may raise the risk are:

  • 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



Most people do not have symptoms of a pinworm infection. Those who do may have:

  • Itching and scratching in the anal area that may be worse at night
  • Problems sleeping


The doctor will ask about symptoms and past health. A physical exam will be done. The doctor may see the pinworms in the area between the anus and genitals. This is enough to make the diagnosis.

Other people may need a tape test to look for pinworm eggs. A person may be asked to do the test at night when the pinworms are most active. A piece of clear tape is placed over the anus and removed. Any eggs will appear on the tape.

The doctor may also look for eggs by taking samples from under a person's fingernails.



A pinworm infection is treated with medicines.


To lower the risk of a pinworm infection:

  • Wash hands well after using the toilet, changing diapers, and before cooking or eating.
  • Keep fingernails short and do not bite them.
  • Do not scratch the area between the anus and genitals.
  • Bathe regularly.
  • Wash underwear regularly.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.