Pinworms, also known as threadworms, are tiny white or light gray worms that cause the common infection called enterobiasis. Usually found in children, pinworm can be treated with anti-parasitic medications that do not require a prescription.


What are pinworms?

Pinworms, also called threadworms, are parasitic worms that live in the intestines and rectums of infected people. Pinworms are small and thin (about ¼ inch to ½ inch long), and white or light gray.


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What is a pinworm infection?

The pinworm infection is called enterobiasis. It is the most common type of worm infection in the United States. Although a pinworm infection does need to be treated, it usually doesn’t cause any serious medical problems.

Pinworm infections are very common, affecting approximately 1 billion people worldwide.

People of all ages can become infected with pinworms, but the infections are found most often in children. Caregivers and family members of infected children have a higher risk of infection.

Day care centers, preschools, and schools are often the source of a pinworm infection. People who live in institutions are also commonly affected by pinworms.

Symptoms and Causes

What are the symptoms of pinworm infections?

Symptoms of a pinworm infection (enterobiasis) include:

  • Anal itching, especially at night: Pinworms lay their eggs around the anus at night, causing itching and irritation. While symptoms are usually mild, anal itching can be severe.
  • Sleeplessness: Because anal itching is worse at night, people suffering from a pinworm infection can have trouble sleeping, which can lead to decreased concentration, tiredness and weight loss.
  • Vaginal itching: In females, symptoms can also include vaginal discharge (seepage) and itching in the vaginal area.


How do people get pinworms?

Pinworm infection occurs when someone swallows pinworm eggs, usually in the following manner:

  1. Pinworms lay their eggs on the skin around the anus of an infected person.
  2. When that person touches or scratches his or her anus, the eggs stick to the fingers and fingernails.
  3. The eggs are then transferred to surfaces and to other people, who swallow them when they touch their mouths.
  4. The eggs travel through the digestive system of the infected person and hatch in the intestines.
  5. Once hatched, the female pinworms make their way to the anus to lay their eggs.

Pinworm eggs can survive for 2-3 weeks on fingers, under fingernails, and on surfaces such as linens, clothing or toilet seats. The tiny eggs can only be seen under a microscope.

Can you get pinworms without being around an infected person?

Yes. A pinworm infection can also be spread through:

  • Bed sheets and undergarments: Eggs can spread through contact with contaminated sheets, towels or underwear of infected people.
  • Inhalation: Because the eggs are so tiny, they can travel through the air and inhaled. Once inhaled, they travel through the digestive tract, hatch and lay their own eggs.
  • Dogs and cats: While pinworms are usually transmitted from human to human, dogs and cats can carry the eggs on their fur and transfer them to humans.


Diagnosis and Tests

How are pinworms infections diagnosed?

If you or your child has anal itching that is worse at night, it’s important to see a doctor. Your doctor will ask about your symptoms, especially anal itching at night. In addition, the doctor may ask you to collect the pinworm eggs using the “tape test.” To do this:

  • Place a clear piece of tape over the anal area as soon as the infected person wakes up in the morning. The eggs will stick to the tape.
  • Take the tape to the doctor, following your doctor’s directions. The eggs will be examined under a microscope.

It’s best to do the tape test as soon as the person wakes up, before bathing or using the bathroom. You should do the tape test a few times to get the most accurate results.

Another way to confirm a diagnosis is to see the pinworms. While the infected person is sleeping, mature pinworms make their way out of the rectum to lay their eggs around the anal opening.

Small, thin, grayish-white worms may be visible around the anus two-three hours after the person falls asleep. The worms look like little pieces of thread, which is why they are sometimes called threadworm. You can capture the worms using clear tape or let your doctor know that you saw them.

Management and Treatment

How are pinworms treated?

Pinworms are treated with an oral (taken by mouth) anti-parasitic medication that kills the worms. You will need to take one dose right away and another dose two weeks later to make sure all the worms are gone. To reduce the risk of re-infection, pediatricians recommend that the family members and caregivers of an infected child be treated, as well.

The medications used to treat pinworms are:

  • Pyrantel pamoate
  • Mebendazole
  • Albendazole

Pyrantel pamoate is the medication most commonly used to treat pinworms. It is available without a prescription (over-the-counter).

What are the side effects of treatment for pinworms?

Before using pyrantel pamoate, you should consult your doctor if you are pregnant or if the infected child is younger than 2 years old. Side effects of pyrantel pamoate include:

For all three medications, side effects include gastrointestinal upset.

What are the complications associated with pinworms?

While serious complications are rare, pinworms can lead to:

  • Bacterial infections: When the infected person scratches the anal area, the skin can bleed and become infected.
  • Urinary tract infections (UTIs): In females, the worms can travel to the vagina and cause infections.
  • Gastrointestinal and abdominal problems: In rare cases, pinworms have been linked to appendicitis, diverticulitis (the growth of pouches in the large intestine), and inflammation of the vagina and the lining of the uterus.

What can I do to help relieve the symptoms of pinworm infections?

To relieve the itching, you can:

  • Wash the anal area with warm water and soap.
  • Use a 1% hydrocortisone cream on the skin around the anus.
  • Avoid scratching the area.


How can I prevent pinworm infections?

The most effective way to prevent a pinworm infection is by practicing cleanliness in the following ways:

  • Wash your hands often: Using soap and warm water, wash your hands after using the bathroom, changing a diaper, before handling food or touching your mouth or nose, and after petting a dog or cat. Make sure your children wash their hands, too.
  • Keep surfaces clean: Clean toys, counters, toilets, utensils, dishes and other surfaces frequently with soap and water to lower the risk of spreading the infection.
  • Shower often: People who have pinworms should shower every day to remove some of the eggs from the skin. Showering is more effective than bathing because bathwater can become contaminated with eggs. People who have pinworms should not bathe with others until the infection is gone.
  • Trim your fingernails: To avoid transferring the eggs, keep your fingernails clean and trimmed.
  • Avoid touching the anal area: Make sure children do not touch or scratch the affected area.
  • Wash sheets, towels and underclothes frequently: Wash linens every day until the treatment is complete. Be careful not to shake out the laundry before washing since eggs can scatter and spread infection.

Outlook / Prognosis

What is the prognosis (outlook) for patients who have pinworms?

With proper treatment, pinworms don’t cause long-term health problems. Children or families can have pinworm infections several times. If the symptoms return after treatment, you should go back to your doctor.

Living With

When should I call my doctor about pinworms?

If you or your child has anal itching that is worse at night, you should contact your doctor or your child’s pediatrician.

Medically Reviewed

Last reviewed on 07/19/2019.

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