Condition Basics

What are pinworms?

Pinworms are a type of parasite that lives in the digestive system of humans. They are common throughout the world.

Adult pinworms are about 0.5 in. (12.7 mm) long and look like little white threads. Pinworm eggs are so tiny, you'd need a microscope to see them.

What causes them?

Most people get infected by accidentally swallowing pinworm eggs. Anyone can get pinworms, but they are most common in school-aged children. They are usually spread like this:

• A child swallows pinworm eggs, and they travel to the child's intestines. In about a month, the eggs hatch into worms. At night the female worms crawl out the rectum and lay eggs around the child's anus.
• When the worms lay eggs, it can cause itching. If the child scratches, the eggs can cling to the child's fingers and get stuck under the fingernails.
• The eggs then stick to things the child touches, such as clothing, dishes, toys, and furniture. The eggs can live 2 to 3 weeks outside the body.
• When you touch something the child has touched, the eggs get on your hands. Then if you touch food or your mouth, you can swallow the eggs. This starts the cycle over again.

Pinworms spread easily in homes, day care centers, schools, and other places where groups of people spend time together. So if one person in your family has pinworms, others probably do too.

It's possible to get pinworms by inhaling airborne eggs, but this is rare. It's also rare to get pinworms from a swimming pool.

Pinworms are spread from person to person. Pets don't get pinworms and can't spread them to humans.

What are the symptoms?

Many people with pinworms don't have symptoms and don't know that they're infected. When symptoms occur, the most common ones are:

• Itching around the anus.
• Restless sleep, because itching is often worse at night.

Pinworms can be annoying. But they don't carry disease, and they rarely cause serious health problems. Sometimes people get a skin infection from scratching.

How are they diagnosed?

To find out if you have pinworms, your doctor will ask about your past health and check the skin around your anus.

The doctor may ask you to do a transparent tape test at home. To do the test, you press a piece of clear, sticky tape on the skin around your anus in the morning before you get up. The doctor will put the tape under a microscope to look for pinworm eggs. You might need to repeat this test a few times.

How are pinworms treated?

You can treat pinworms with over-the-counter or prescription medicine that kills the worms. Treatment can help keep you from getting infected again and from spreading the infection to other people.

You will probably need two doses, 2 weeks apart. That's because the medicine kills the worms but not the eggs. The second dose will kill any worms that hatch after the first treatment.

Pinworm medicine may not be safe for children younger than 2 and women who are pregnant or breastfeeding. So to reduce their risk of infection, a doctor may recommend that all other household members be treated with medicine.

How can you prevent them?

Pinworms spread easily and often come back. To reduce your chances of spreading the infection or getting infected again:

• Wash your hands carefully and often. Teach your children to do the same, especially after they use the toilet and before they handle food.
• Keep your fingernails short, and don't scratch the itch. Wearing gloves at night may help prevent scratching.
• Bathe or shower every day.
• Don't share or reuse towels or washcloths.
• Change your underwear and bedding each morning.
• Wash clothes, bedding, and towels regularly. Dry them in a hot dryer.

If anyone in your household gets pinworms again, the whole family may need to take medicine.