The most common symptom of a pinworm infection is intense itching around the anus. Infections are contagious but are preventable with handwashing and other hygiene practices.

A pinworm, or Enterobius vermicularis, infection is a common human intestinal worm infection.

Pinworm infections can spread easily. They most commonly occur in school-aged children and people who live in close quarters. They also occur often in those who have regular, close contact with individuals in these groups.

Medication can effectively treat pinworm infections, though reinfection is possible. Serious complications and long-term health effects are rare.

Learn more about the signs of a pinworm infection and some steps to take to help prevent pinworm infection.

The most common symptom of a pinworm infection is intense itching around the anus.

Other symptoms can include:

  • strong, frequent itching of the anal area
  • restless sleep due to anal itching and discomfort
  • pain, rash, or other skin irritation around the anus
  • pinworms in your anal area
  • abdominal pain

Many individuals with pinworm infections may not experience any symptoms.

Pinworms are tiny, parasitic nematodes that live in the intestines and lay eggs on the skin around the anus. They are named for the pin-like tail on the female worms.

These white to beige worms appear thread-like.

A fully matured adult female pinworm measures around 8 to 13 millimeters (mm). Adult male pinworms measure around 2 to 5 mm.

Pinworm infections are highly contagious. When the person with a pinworm infection scratches the affected area, the eggs transfer to the fingers and under the fingernails. The eggs can transfer to anything the person touches and survive on an indoor surface, such as bedding or clothing, where they can survive for around 2 to 3 weeks.

Coming into contact with the eggs and then eating can lead to ingesting pinworm eggs.

While rare, it is also possible to inhale airborne eggs. This could happen when shaking contaminated bedding, towels, or clothing.

The infection cycle typically follows these steps:

  1. Generally, an individual gets a pinworm infection through the fecal-oral route. For example, this can happen if a person with the infection prepares or handles foods, and then somebody eats that food.
  2. The eggs remain in the small intestine until they hatch and mature.
  3. Adult female pinworms move into the colon and exit the body through the anus at night. They lay eggs in the folds of skin around the anus.

Sometimes eggs on the anus hatch, and the larvae can reenter the large intestine. Without treatment, this can cause the infection to continue indefinitely.

Pinworm infections are highly contagious, especially among people in close quarters, such as a school.

Children can transfer pinworm eggs easily because they may put toys or objects containing pinworm eggs in their mouths.

Pinworm infections can affect people of all ages, but they are more common in school-aged children. Since pinworm eggs are so small, it can be difficult to avoid individuals or areas with the infection.

While anyone can get a pinworm infection, the following groups can be more susceptible:

  • children who attend day care, preschool, or elementary school
  • people who chew their fingernails
  • individuals who live in crowded accommodations, such as institutions or dormitories
  • people who may not practice regular handwashing prior to eating
  • family members or caregivers of people with a pinworm infection
  • people who live in tropical climates

Only humans can get a pinworm infection. Cats, dogs, and other animals can’t acquire or transmit them.

It’s not necessary to treat your pets for pinworm infection, even if people in your household may have pinworms.

However, you should contact a vet if you have concerns about worms or other illnesses affecting your pets.

A tape test is a reliable method for diagnosing a pinworm infection. This test involves pressing the sticky, adhesive side of clear cellophane tape against the skin around the anus.

Because pinworms often exit the anus while a person sleeps, people who suspect they have an infection should conduct a tape test immediately upon waking in the morning. Bathing or using the toilet can remove the eggs from your skin, so perform the test before you do anything else. If eggs are present, they should stick to the tape.

Take the tape to a doctor, who will examine it under a microscope to see if it contains pinworm eggs.

You may need to do the test for 5 mornings in a row before a doctor can rule out the condition.

Medications and household cleaning strategies can help eliminate pinworms.

Medication

You can treat pinworm infections with either over-the-counter or prescription oral medications. Talk with a doctor to determine which is best for you.

The most common and effective medications to treat pinworm infections include:

  • mebendazole (Vermox)
  • albendazole (Albenza)
  • pyrantel pamoate

Since pinworms easily pass from one person to another, all household members of a person with an infection — as well as caregivers and anyone else in close contact — may need treatment to prevent a pinworm infection or reinfection.

One course of medication usually involves an initial dose followed by a second dose 2 weeks later. More than one course might be necessary to fully eliminate the eggs.

Creams or ointments can help soothe itchy skin.

Household cleaning

In addition to medication, a hygiene and household cleaning regimen such as the following can help you remove pinworm eggs:

  • Ensure the person with the infection and other household members thoroughly wash their hands with soap and warm water, especially before eating.
  • Encourage household members to shower and change their underwear every morning. It is best to avoid bathing.
  • Maintain clean, short fingernails.
  • Avoid biting your nails.
  • Tell the person with the infection to avoid scratching the anal area.
  • Use hot water to launder all bedding, towels, washcloths, and clothing. Dry on high heat.
  • Avoid shaking clothing and bedding to keep pinworm eggs from spreading through the air.
  • Do not allow children to bathe together, as pinworm eggs can potentially spread in bath water and on washcloths.
  • Thoroughly clean any surfaces that might have eggs, such as toys, floors, countertops, and toilet seats.
  • Carefully vacuum all carpeted areas.

Most people don’t experience serious complications from pinworm infections, but occasionally the following complications can occur:

The best way to prevent pinworm infections and repeat infections is to follow these hygiene routines and encourage other household members, especially children, to do the following:

  • Wash your hands carefully with soap and warm water after using the toilet, especially after bowel movements, after changing diapers, and before preparing and eating food.
  • Keep your fingernails short and clean.
  • Avoid habits that could spread pinworm eggs, such as nail biting or scratching.
  • Shower every morning to remove eggs deposited overnight, if you can.
  • Change your underwear and clothing daily.
  • Use hot water in the washing machine and hot air in the dryer when laundering bedding, clothing, and towels, if possible.

It’s possible to treat a pinworm infection with medication and a diligent cleaning regimen. However, because pinworm eggs are invisible to the naked eye and highly contagious, repeat infection can easily occur.

A pinworm infection can be acquired again when a pinworm larva hatches and reenters the anus. Reinfection can also occur if pinworm eggs are ingested. This can happen if pinworm eggs are on the hands or if the eggs become airborne.

A pinworm infection is a common intestinal infection. It is contagious and tends to affect school-age children and those in group settings, like nurseries or group homes.

The most common symptom is intense itching around the anus.

Pinworm infection is treatable with medication and household cleaning. However, repeat infection is possible.

Speak with a doctor if there are concerns about a possible pinworm infection or recurrence.