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Pinworm infection

Published on March 8, 2024 at 8:00 / Updated on March 26, 2024 at 8:00

Pinworm infection (also called enterobiasis or oxyuriasis) is a common intestinal infection caused by a parasite. It usually affects children, their caregivers, and their family members. Although unpleasant, it rarely causes serious health problems.

The parasite that causes this infection is called a pinworm, also known as Enterobius vermicularis. Adult pinworms resemble tiny white threads that measure about 0.5 cm long. The eggs are invisible to the naked eye; they can only be seen using a microscope.

Causes and triggers

Pinworm infection is caused by the ingestion of pinworm eggs. This generally occurs through contact with an infected person or contaminated objects. In very rare cases, infection can also result from swimming pool use or inhalation of airborne eggs. Pinworms do not infect pets, only humans.

Children have a higher risk of infection. They aren't yet in the habit of washing their hands regularly and often put their hands in their mouths. This can lead to reinfection. Also at risk is anyone in close contact with an infected person, including:

  • Someone living in the same house as the infected person
  • Someone who takes care of the infected person (e.g., at school, at daycare, in a health care facility)


The main symptom is itching which can sometimes be intense. It is caused by a substance that the female pinworm uses to stick her eggs around the anus during the night. In many cases, the infected person will experience no symptoms. For others, the itching can be bad enough to cause difficulty sleeping. Some may even develop a skin infection from scratching. In cases of severe infection, symptoms can include:

  • Stomach pains
  • Irritability
  • Loss of appetite
  • Nausea and vomiting

Pinworms reach maturity after 1 to 2 months. It can therefore take up to 60 days from infection for the first symptoms to appear. At the onset of symptoms, the anal area should be checked 2 to 3 hours after the infected person falls asleep. If no parasites are visible, the tape test can be done.

Tape test

The test should be done in the morning upon waking.
Use fully transparent tape.
Press a strip of tape to the skin around the anus several times.
Place the tape in a glass jar or plastic bag.
If necessary, repeat this test over 3 or more consecutive days to collect the eggs, using a new strip of tape each time.
Bring the samples to a medical clinic to be examined under a microscope.


Pinworm infection is treated with medication under the supervision of a pharmacist. Two doses are given 14 days apart to prevent reinfection. It may be necessary to treat anyone living with the infected person as well as their sexual partners, if applicable, even if they have no symptoms. Note that symptoms may continue for a week after the start of treatment. A soothing cream may be recommended to relieve itching.

Pinworm eggs can survive for up to 3 weeks in the home. The following measures are recommended during treatment and should also be taken to prevent reinfection:

  • Wash your hands thoroughly before meals
  • Wash your hands thoroughly after going to the bathroom or changing a diaper
  • Shower or bathe in the morning to remove as many eggs as possible
  • Keep your nails short and avoid biting them
  • Avoid scratching between your legs and buttocks
  • Do not share clothes, towels, or bedding
  • Change your underwear every day
  • Wash your sheets often and machine dry them on high heat
  • Avoid shaking dirty laundry and bedding to keep from dispersing eggs into the air
  • Wash or vacuum objects that are most likely to be contaminated (e.g., toys, door handles, toilet seats, the floor around the bed)
  • Open the blinds or curtains in bedrooms during the day, as sunlight will kill any exposed eggs

When should I see a health care professional?

Speak with your health care provider if you or your child is experiencing any of the following:

  • Itching around the anus, especially at night
  • A skin infection from scratching
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