Pinworms (enterobiasis)

Pinworms are one of the most common worm conditions. They are particularly common in children. The worms settle in the human colon. An infection is usually harmless, but can cause an unpleasant itching in the anal area.

At a glance

  • Pinworm infections (enterobiasis) occur particularly in children of kindergarten/pre-school and elementary/primary school age.
  • Pinworms are tiny worms that can live in the colon of humans.
  • The infection is usually harmless and often causes no problems.
  • The most common symptom is itching in the anal area.
  • The itching is caused by female worms that move from the colon to the rectum and lay their eggs in folds of skin around the anus.
  • A key hygiene measure in preventing the spread of pinworms is thorough hand washing, especially before eating and after going to the toilet.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

A child in underwear clutching at their bottom. A toilet in the background.

What are pinworms?

Pinworms cause one of the most common worm conditions in humans. They affect children in particular.

The tiny, white-beige parasites make their home in the human bowel. The females are around one centimeter long, the males smaller.

Pinworms are spread by swallowing worm eggs that may be on hands, toys or food, for example. When a child holds things that the worms are stuck to and then puts their fingers in their mouth, the eggs then travel to their bowel.

Thorough hand washing with soap and water helps prevent infection – this is particularly important after going to the toilet and before eating.

What symptoms can pinworms cause?

Pinworms usually go unnoticed. If the worms cause symptoms, it is usually itching in the rectal and anal area. This usually happens at night and can disrupt sleep.

The most common symptom of pinworms is itching around the anus.

Large amounts of worms in the bowel can sometimes cause stomach pain, nausea and vomiting.

Scratching can cause minute skin damage around the anus, which provide a point of entry for bacteria and can become inflamed.

Very occasionally, in girls, the worms move from the anus via the skin to the vaginal area and cause inflammation there.

How do people get pinworms?

People get pinworm infections by accidentally swallowing worm eggs. This can happen when someone handles objects that worm eggs are clinging to, and then put their hand to their mouth, or when children put toys or pencils with worm eggs clinging to them into their mouths.

Shortly after, worm eggs get into the stomach, the worm larvae hatch and move to the small intestine. There, the larvae develop into worms. The adult worms are mainly found in the colon. The males die shortly after fertilizing the females, while the females can live for up to 100 days. To lay their eggs, they move into the rectum and leave the intestines through the anus, particularly at night. The movement of the worms is the reason for the itching.

The eggs are sticky and cling to the folds of skin around the anus. Scratching causes the worm eggs to get onto the hands and under the fingernails. When a child then handles objects, the worm eggs can spread and infect other people. If they put their fingers in their mouth, they can infect themselves again.

Interesting fact: The pinworm only infests humans, so it is not spread by pets.

Which factors make a pinworm infection more likely?

Many children of kindergarten/pre-school or elementary/primary school age get infected. The worm eggs can spread due to close contact with other children and children holding toys and putting them in their mouth.

Not washing hands before eating or after going to the toilet helps the spread. Chewing fingernails also increases the likelihood of infection.

When someone in the family has worms, other family members can easily become infected too.

Factors that favor pinworm infection: close contacts, handling toys, putting toys in the mouth, not washing hands, biting fingernails.

How common are pinworms?

In Western Europe, around 20 percent of children of kindergarten/pre-school and elementary/primary school age have pinworms. It is the most common type of worm infection. The worms are less common in children below the age of 2, those aged over 14 and adults.

How are pinworms diagnosed?

Symptoms such as itching in the anal area typically indicate a pinworm infection.

The tiny worms can sometimes be seen in underwear and pajamas, on bedding, or in folds of skin around the anus. However, worms and worm eggs are not always visible to the naked eye.

When a worm infection is suspected, it is a good idea to consult a doctor.

Adhesive strips that can be pressed onto the skin around the anus, ideally in the morning before washing and before going to the toilet, can be used to reveal worm eggs. The adhesive strips are then stuck to a glass plate and the doctor examines them under a microscope. The eggs, if present, will be visible under a microscope.

How are pinworms treated?

If the pinworms are not treated, children can infect themselves again and again. This is why worms do not usually disappear by themselves. However, there are medications that kill off the intestinal worms and allow the infection to clear up.

Medications can be used to kill off intestinal pinworms so that the infection clears up more quickly.

These can be taken in tablet or syrup form and are not usually unpleasant. Occasionally they cause diarrhea, headaches or stomach aches.

To prevent further infection, the treatment should be repeated after 2 weeks and 4 weeks, because a child can easily become infected again as infectious eggs often still remain in the area.

Simple hygiene measures help prevent re-infection and the spread of pinworms to other people. These include:

  • cutting fingernails short and not biting them
  • frequent hand washing
  • washing or showering every morning
  • not scratching the anal area
  • changing underwear each day
  • frequent washing of pajamas and bedding

If pinworm infections occur repeatedly despite the treatment, all family members may need to be treated.

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen – IQWiG). As at:

Did you find this article helpful?