The pinworm, also known as threadworm, is a common intestinal parasite. It mostly occurs in children and leads to itching around the anus. A pinworm infestation is known as enterobiasis.

According to the Centers for Disease Control and Prevention (CDC), pinworms are the most common type of worm infection in the United States.

Pinworms are parasites. They use the human body to survive and reproduce. Human pinworms cannot infect any other animals.

Adult female worms are 8–13 millimeters (mm) long, and males are 2–5 mm. They are whitish in color and look like small pieces of thread. They live for 2–3 weeks.

Effective treatment is available that can eliminate pinworms.

Here, find out how to recognize a pinworm infestation and how to treat it.

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Some people have no symptoms. If they occur, the main symptom is itching around the anus that can disturb sleep. This occurs 1–2 months after the pinworms enter the body, during the maturing and reproduction stage.

There may also be:

  • insomnia due to disturbed sleep
  • abdominal pain
  • infection of the female genital tract
  • a secondary infection due to scratching
  • irritability due to itching

If an individual only has a small number of adult worms, the symptoms will be mild, or there may be no symptoms. Symptoms are worse with a more severe infection.

Treatment is with medication, such as:

  • mebendazole
  • pyrantel pamoate, available without prescription
  • albendazole

A person will need one dose at the beginning and another dose of the same drug 2 weeks later. This will prevent reinfection, because the drugs do not kill the eggs.

If one member of a household has an infection, all members should receive treatment.

Speak with a doctor if a child under 2 years needs treatment. The doctor can recommend the safest and most effective approach for the child’s age.

Strict hygiene measures can remedy pinworm infection and significantly reduce the risk of reinfection.

Tips include the following:

  • Practice careful handwashing techniques, especially after using the bathroom, changing diapers, and handling food.
  • Shower every morning to wash off any eggs. Showering is better than bathing as it prevents eggs passing onto the bath.
  • Keep the fingernails clean to prevent reinfection.
  • Avoid scratching around the anus.
  • Avoid putting the fingers in the mouth.
  • Wash bed linen and underclothes in hot water in the morning after waking up. Do not shake them but move them straight to the washer. Dry with a hot dryer.

When the infestation has gone, good handwashing practices and hygiene will help prevent reinfection. Good hygiene can prevent another outbreak even if children pick up another pinworm infection from friends at school.

If a person with a pinworm infection touches their underwear, bedsheets, or their anus, they can pick up eggs on their fingers.

If they touch another surface, they can leave the eggs there. Anyone who touches that surface and then touches their mouth is at risk of infection. Eggs can live on a surface for 2 weeks.

The female pinworm lays eggs around the anus and vagina. The eggs can be transferred from the person’s anus to:

  • bed sheets
  • carpets
  • hands
  • towels
  • underwear and clothes

The female pinworm releases an itchy mucus when laying eggs, triggering an urge to scratch the affected area of the anus or vagina. From the hands, the eggs can pass on to anything that is touched, including:

  • bathroom utensils, such as toothbrushes, combs, and brushes
  • other people’s hands
  • furniture
  • kitchen and bathroom surfaces
  • kitchen utensils
  • toys

To diagnose a pinworm infection, a doctor may use the following:

Tape test

The doctor places a piece of clear plastic tape against the skin around the anus and then looks at the tape under a microscope. As the worm tends to lay eggs at night, good samples are more likely early in the morning. People may apply the tape at home and take or send the sample to the doctor.

Moistened swab

A doctor or nurse may take a moistened swab around the anal area.

Sighting a worm

Sometimes worms are visible in the anal area, on underwear, or in the toilet. In stool, they look like small pieces of white cotton thread.

To examine a child, inspect the anal area 2–3 hours after going to sleep, when the females are active outside the anus.

If there is no evidence of pinworms for 5 consecutive mornings, a doctor will not diagnose a pinworm infection.

Anyone who believes they have a pinworm infection should seek medical advice.

People should take extra care if they:

  • are pregnant
  • are breastfeeding
  • have a baby less than 6 months of age

Occasionally, complications can arise, for instance:

  • a secondary bacterial infection due to scratching
  • urinary tract infection
  • appendicitis, if the infection lasts a long time and there is no treatment

Here are some questions people often ask about pinworms.

How can you tell if you have pinworms?

The main symptom of pinworms is itching around the anus, especially at night.

How does a person get pinworms?

A person can take in the eggs by touching a surface that another person — who has an infection and has eggs on their fingers — has touched. Less commonly, they can take them in by shaking out bedding and breathing in and swallowing eggs in the air.

Do pinworms go away without treatment?

To treat pinworms, a doctor may recommend two doses of medication, 2 weeks apart and following strict hygiene practices to avoid reinfection. One medication, pyrantel pamoate, is available without a prescription. A doctor may not recommend medication for children under 2 years.

A pinworm infection happens when the eggs of a pinworm enter a person’s intestine. As the females mature, they move to the anal area. At night, they leave the anus and lay eggs in the area around it.

Some people have no symptoms, but it can cause severe itching. In the long term, more severe complications can occur.

Not everyone needs treatment for an infection, but two doses of medication 2 weeks apart can eliminate pinworms.