Pinworm is an intestinal infection caused by tiny parasitic worms. One of the most common roundworm infections, pinworm infections affect millions of people each year, particularly schoolkids.

But if your child develops a pinworm infection, don't worry. Pinworms don't cause any harm (just itching), and it won't take long to get rid of them. And people who have pinworms aren't dirty — kids can get pinworms no matter how often they take a bath.

How Pinworm Infections Spread

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

People become infected by unknowingly ingesting microscopic pinworm eggs that 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 continue their journey to the large intestine, where they live as parasites — their heads attached to the inside wall of the bowel.

About 1 to 2 months after a person acquires the pinworm eggs, adult female pinworms begin migrating from the large intestine to the area around the rectum. There, they will lay new pinworm eggs, which trigger itching around the rectum.

When someone scratches the itchy area, microscopic pinworm eggs are transferred to their fingers. Contaminated fingers can then carry pinworm eggs to the mouth, where they are reingested, or to 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.

Signs and Symptoms

Often, someone can have a pinworm infection without having any symptoms. When symptoms are present, the most common one is itching around the rectum and restless sleep. The itching is usually worse at night and is caused by worms migrating to the area around the rectum to lay their eggs. In girls, pinworm infection can spread to the vagina and cause a vaginal discharge. If the itching leads to broken skin, it can also become a secondary 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 might also see the worms in the toilet after he or she 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.

Abdominal pain and nausea are less common symptoms but can occur if there is a high population of pinworms in the intestines.

Diagnosis and Treatment

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

If your child has a pinworm infection, the doctor may prescribe an antiworm medication that is given in one dose and repeated in 2 weeks. The doctor may decide to treat the entire family, especially if it is a recurrent infection.

Although medicine takes care of the worm infection, the itching may last about a week after medicine is taken. So the doctor may also give your child a cream or other medication to help stop the itching.

Frequent hand washing and routine household cleaning measures (including frequent changing of underwear, and washing everyone's pajamas and bed linens) also will help reduce the spread of pinworm infection to the family.

When to Call the Doctor

Call the doctor if your child complains of an itchiness or he or she 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 urine leaves the bladder and exits the body — and lead to bedwetting.)

Prevention

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 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.

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

Reviewed by: Yamini Durani, MD
Date reviewed: May 2011