Pinworm Infestation

A pinworm infestation is caused by a type of roundworm known as Enterobius vermicularis.

What is going on in the body?

Pinworm infestation occurs all over the world. Humans are the only known hosts. A person gets pinworms by swallowing the eggs of the worm. Pinworm eggs remain alive for up to three weeks.

Pinworms generally find a home in the colon, or large intestine. At night, they come through the anus to lay their eggs on the surrounding skin outside of it. Sometimes the worms migrate to other areas of the body, including the following:

After leaving the colon to lay eggs or migrate to other parts of the body, the worms usually die. However, children and adults can sometimes reinfect themselves.

What are the causes and risks of the condition?

A pinworm infestation occurs when people swallow the eggs of the roundworm known as Enterobius vermicularis. Pinworm eggs can live for up to two weeks on clothing, bedding, toys, and other objects. A person can get a pinworm infestation by swallowing eggs from these surfaces. An individual can also be infested from fingers contaminated with the stool of an infected person.

School-age children and preschoolers are most prone to pinworm infestations. Mothers of infected children often become infested with pinworm. Other adults are less likely to have pinworms.

What are the signs and symptoms of the condition?

An itchy anus is the most common symptom of a pinworm infestation. It is caused by the adult worm migrating out through the anus to lay eggs. This usually occurs at night, which is when the itching will be most intense. The first signs and symptoms may not appear until one to two months or more after the person swallows the pinworm eggs.

A child with pinworms may have sleep disturbances. The child may be irritable because of the itching and poor sleep. If the infestation is severe, the person may be restless and have a poor appetite.

How is the condition diagnosed?

Pinworms are diagnosed by finding the adult worms in the stool or around the anus. The worms are most visible two to three hours after the person goes to sleep. One way to check for eggs is to briefly place and remove a piece of clear adhesive tape over the anus. The tape can then be examined for signs of pinworms directly or with a microscope.

What can be done to prevent the condition?

The spread of pinworm infestation can be minimized by good handwashing. This is especially important after using the toilet or changing diapers. Children should be discouraged from biting their nails or scratching the anal area.

What are the long-term effects of the condition?

Pinworm infestations generally clear up on their own or with treatment, without any long-term effects.

What are the risks to others?

Pinworm infestations can be transmitted from person to person by contaminated hands or objects.

What are the treatments for the condition?

Treatment is not usually needed, though parents are often concerned about the pinworms in their children. A combination of the medications mebendazole and pyrantel pamoate is used. The medications are given in two separate doses, two weeks apart. All family members should also take the medications to rid them of pinworms.

What are the side effects of the treatments?

The medications used to treat pinworm infestations may cause diarrhea, abdominal distress, headache, dizziness, and rash.

What happens after treatment for the condition?

The pinworm infestation usually goes away, with or without treatment. If a person has repeated episodes of pinworms, it's important to look for the source of the new infestations.

How is the condition monitored?

Any new or worsening symptoms should be reported to the healthcare provider.

Author:Danielle Zerr, MD
Date Written:
Editor:Ballenberg, Sally, BS
Edit Date:03/30/01
Reviewer:Eileen McLaughlin, RN, BSN
Date Reviewed:08/06/01