Overview of Pinworms

Pinworms are slender, white, threadlike worms, about a third of an inch long, that can infest the intestinal tract. Infestation with these parasites begins when pinworm eggs are swallowed and lodge in the intestine, where they hatch and mature. Two to six weeks later, the adult worm exits the anus to lay new eggs, often during the night when a person is sleeping.

Pinworms are more of a nuisance than a serious health problem. The main complaint is intense anal itching, due to the irritation caused by worms migrating across the skin. In general, the body’s immune system eliminates pinworms living in the intestine within several months. However, eggs are usually dispersed in bedding material or clothing and may spread via the fingers or even through the air, making reingestion of eggs and a new cycle of infestation common—not just among those who were originally affected but among other members of the household as well. Pinworms are very common, affecting up to 10 to 15 percent of the population, especially children.

What Causes Pinworms?

  • Swallowing pinworm eggs initiates a cycle of infection. Most often, eggs are spread when a child scratches the anus, allowing the eggs to be transported on the fingers or beneath the fingernails, where they can then contaminate food, dishes, toys, or play areas.

Symptoms of Pinworms

  • Anal itching or pain
  • Irritability or fidgetiness
  • Restless sleep
  • Sleeping disorder
  • Loss of appetite
  • Unexpected weight loss
  • Being nervous and irritated
  • Vaginal itching, pain, or discharge. This occurs infrequently when adult worms migrate across the skin to the vagina.

Preventing Pinworms

  • It is difficult to prevent an initial outbreak of pinworms. However, the following measures can be used to prevent reinfestation once the first outbreak has occurred:
  • Wash the hands thoroughly before eating, after using the restroom and after handling potentially infected objects, such as children’s toys.
  • Keep fingernails short so they are less likely to pick up eggs.
  • Avoid nail-biting and scratching the anal area.
  • Shower daily in the morning.
  • Open bedroom blinds and curtains during the day. Eggs are sensitive to sunlight.
  • Change and wash your underwear, pajamas and bedding every day.
  • Maintain cleanliness in the bathrooms and bedrooms.

Diagnosis of Pinworms

  • Adult worms are sometimes seen around the anal area at night or in bowel movements. A doctor can supply a piece of cellulose tape to be applied to the anal area during the night or in the early morning. The tape is then examined under a microscope for worms or eggs to confirm the diagnosis. Specimens from three consecutive mornings may be necessary to confirm the diagnosis.

How to Treat Pinworms

  • Usually, a single dose of mebendazole or pyrantel pamoate is given, followed by a repeat dose two weeks later. These medicines are very effective in killing worms.
  • Creams or ointments that relieve anal itching and that may contain substances that kill the worms can be prescribed.
  • There is a high risk of reinfection and recurrence is common. If repeated infections occur, members of the whole household should be treated.

When to Call a Doctor

  • Call a doctor if symptoms of pinworm infestation occur.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at HealthCommunities.com

Published: 24 Aug 2011

Last Modified: 12 Feb 2015