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What Is a Pinworm Infection?

Pinworm is an intestinal infection caused by tiny parasitic worms. It's a common infection that affects millions of people each year, particularly school-age kids.

If your child develops a pinworm infection, try not to worry. Pinworms don't cause any harm (just itching and restless sleep), and it won't take long to get rid of them.

How Do Pinworm Infections Spread?

Pinworm infections (also known as "seatworm infection" or "threadworm infection") are contagious.

Pinworms get into the body when people ingest or breathe in the microscopic pinworm eggs. These eggs can be found on contaminated hands and surfaces, such as:

bed linens

towels

clothing (especially underwear and pajamas)

toilets

bathroom fixtures

food

drinking glasses

eating utensils

toys

kitchen counters

desks or lunch tables at school

sandboxes

The eggs pass into the digestive system and hatch in the small intestine. From the small intestine, pinworm larvae go to the large intestine, where they live as parasites (with their heads attached to the inside wall of the bowel).

About 1 to 2 months later, adult female pinworms leave the large intestine through the anus (the opening where bowel movements come out). They lay eggs on the skin right around the anus, which triggers itching in that area. Often, this happens at night.

When someone scratches the itchy area, microscopic pinworm eggs transfer to their fingers. Contaminated fingers can then carry pinworm eggs to the mouth, where they go back into the body, or stay on various surfaces, where they can live for 2 to 3 weeks.

If you're wondering if your family pet could give your child a pinworm infection, it can't. Pinworms don't come from animals.

What Are the Signs & Symptoms of Pinworm Infection?

The most common signs of a pinworm infection are itching around the anus and restless sleep. The itching is usually worse at night because the worms move to the area around the anus to lay their eggs. In girls, pinworm infection can spread to the vagina and cause a vaginal discharge. If the itching breaks the skin, it also could lead to a bacterial skin infection.

If your child has a pinworm infection, you can see worms in the anal region, especially if you look about 2 or 3 hours after your child has fallen asleep. You also might see the worms in the toilet after your child goes to the bathroom. They look like tiny pieces of white thread and are really small — about as long as a staple. You might also see them on your child's underwear in the morning.

Belly pain and nausea are less common symptoms but can happen if there are many pinworms in the intestines.

How Are Pinworm Infections Diagnosed?

Your doctor may ask you to help make the diagnosis of pinworm by placing a sticky piece of clear cellophane tape against the skin around your child's anus. Pinworm eggs will stick to the tape and can be seen under a microscope. The best time to do this is at night or in the morning before a bath (when there's the most pinworm activity around the anus). The doctor also might take some samples from under a child's fingernails to look for eggs.

How Are Pinworm Infections Treated?

If your child has a pinworm infection, the doctor will recommend an over-the-counter or prescription antiworm medicine. This is given in one dose and repeated in 2 weeks. The doctor may decide to treat the entire family, especially if your child has had a pinworm infection before.

Although medicine takes care of the worm infection, the itching may continue for about a week. So the doctor also might give your child a cream or other medicine to help stop the itching.

Regular hand washing and routine household cleaning (including frequent changing of underwear, and washing everyone's pajamas, towels, and bed linens) also will help prevent the spread of a pinworm infection within the family.

Can Pinworm Infections Be Prevented?

Here are a few ways to prevent pinworm infections in your family:

Remind kids to wash their hands often, especially after using the toilet, after playing outside, and before eating.

Make sure your kids shower or bathe every day and change underwear and swimsuits daily.

Keep kids' fingernails short and clean.

Tell kids not to scratch around their bottom or bite their nails.

Wash your kids' pajamas every few days.

When Should I Call the Doctor?

Call the doctor if your child complains of itchy skin or always seems to be scratching the anal or vaginal area.

Also ask about whether pinworms could be to blame if your child has trouble sleeping or has begun to wet the bed. (Pinworms can irritate the urethra — the channel through which pee leaves the bladder and exits the body — and lead to bedwetting.)

Remember that pinworms are quite common among kids and aren't harmful. By taking medicine and following some prevention tips, you'll be rid of the worms in no time.