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Pinworms

Pinworms are small worms that infect the intestines.

Alternative Names

Enterobiasis; Oxyuriasis; Threadworm; Seatworm; Enterobius vermicularis; E vermicularis; Helminthic infection

Causes, incidence, and risk factors

Pinworms are the most common worm infection in the United States. They are most common in school-age children.

Pinworm eggs are spread directly from person to person. They can also be spread by touching bedding, food, or other items contaminated with the eggs.

Typically, children are infected by unknowingly touching pinworm eggs and putting their fingers in their mouths. The eggs are swallowed, and eventually hatch in the small intestine. The worms mature in the colon.

Female worms then move to the child's anal area, especially at night, and deposit more eggs. This may cause intense itching. The area may even become infected. When the child scratches the itching anal area, the eggs can get under the child's fingernails. These eggs can be transferred to other children, family members, and items in the house.

Symptoms

  • Difficulty sleeping due to the itching that occurs during the night
  • Intense itching around the anus
  • Irritability due to itching and interrupted sleep
  • Irritated or infected skin around the anus, from constant scratching
  • Irritation or discomfort of the vagina in young girls (if an adult worm enters the vagina rather than the anus)
  • Loss of appetite and weight (uncommon, but can occur in severe infections)

Signs and tests

Pinworms can be spotted in the anal area, especially at night when the worms lay their eggs there.

Your doctor or nurse may have you do a tape test . A piece of cellophane tape is pressed against the skin around the anus, and removed. This should be done in the morning before bathing or using the toilet, because bathing and wiping may remove eggs. The doctor will stick the tape to a slide and look for eggs using a microscope.

Treatment

Anthelmintic (anti-worm) medicines are used to kill the pinworms (not their eggs). Your doctor or nurse will likely recommend one dose of mebendazole or albendazole. These are available over-the-counter and by prescription.

More than one household member is likely to be infected, so the entire household is often treated. Another dose is usually repeated after 2 weeks. This treats worms that hatched since the first treatment.

To control the eggs:

  • Clean toilet seats daily
  • Keep fingernails short and clean
  • Wash all bed linens twice a week
  • Wash hands before meals and after using the toilet

Avoid scratching the infected area around the anus. This can contaminate your fingers and everything else that you touch.

Keep your hands and fingers away from your nose and mouth unless they are freshly washed. Be extra careful while family members are being treated for pinworms.

Expectations (prognosis)

Pinworm infection is fully treatable.

Calling your health care provider

Call for an appointment with your health care provider if:

  • You or your child has symptoms of pinworm infection
  • You have seen pinworms on your child

Prevention

Wash hands after using the bathroom and before preparing food. Wash bedding and underclothing frequently, especially those of any affected family members.

References

Dent AE, Kazura JW. Enterobiasis (Enterobius Vermicularis). In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 286.

Updated: 11/28/2012

A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang. Previously reviewed by Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington (8/14/2012).


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