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What are pinworms?

Pinworms are a type of parasite that lives in the digestive system of humans. They are common throughout the world, especially in school-age children.

Adult pinworms look like small, white threads that are no more than 0.5 in. (12.7 mm) long. You need a microscope to see the eggs.

What causes pinworms?

Most people get pinworms by swallowing the worms' eggs. This happens when someone with pinworms scratches around the anus, gets eggs on his or her hands (or under the fingernails), and touches you or a surface that you later touch. When eggs get on your hands or food and then you eat, the eggs go into your mouth. And they move into your stomach and then to your rectal area.

The eggs turn into worms in about a month. A pinworm crawls out of the body during the night and lays eggs on the skin around the anus. The wiggling motion when the worm lays eggs may irritate the skin and cause itching.

Pinworms spread easily in families, day care centers, schools, camps, and other places where groups of people live. If one person in your family has pinworms, others probably do too. Pinworm infections can happen to anyone. They are not related to being unclean.

What are the symptoms?

The most common sign of pinworms is itching around the anus. Many people with pinworm infections have no symptoms and may never be aware of the infection. In rare cases, itching becomes severe and may cause restless sleep, loss of appetite, and anxiety.

Pinworms don't usually cause serious health problems, and they do not carry disease. But it is possible to get a skin infection from scratching around the anus.

The incubation period-the time from first contact with eggs until symptoms appear-is usually 1 to 2 months or longer.

How are pinworms diagnosed?

Your doctor can find out if you have a pinworm infection by asking about your past health and checking the skin around your anus. He or she may ask you to collect a sample from around the anus by using a piece of clear, sticky tape. This piece of tape will be put under a microscope to look for pinworm eggs.

How are they treated?

You can treat pinworm infections with over-the-counter and prescription medicines. These medicines can help keep you from getting infected again and from spreading pinworms to other people.

How do you keep from spreading pinworms or getting them again?

To limit the chances of getting pinworms or of spreading them to others:

  • Wash your hands carefully and often.
  • Avoid scratching around your anus.
  • Keep your fingernails short.
  • Wash clothes and bedding regularly.
  • Bathe and change your underwear every day.

If family members get pinworms again, all family members may need to take medicine to kill pinworms.

Frequently Asked Questions

Learning about pinworms:

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Getting treatment:

Ongoing concerns:


WebMD Medical Reference from Healthwise

Last Updated: September 02, 2010
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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