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What are pinworms? Pinworms are tiny white worms (Enterobius vermicularis) that live in the intestine. They are about the length of a staple. Pinworms are sometimes called threadworms because they look like a piece of white thread.


  • Pinworms Fact SheetPinworms Fact Sheet (PDF 79KB)
    View, download and print the Pinworms Fact Sheet.  Pinworms are sometimes called threadworms because they look like a piece of white thread.

Contact Us

For more information, please contact the Infectious Disease Control Team:

  • 519-663-5317 Ext. 2330

Who is at risk?

Pinworm infection affects people of all ages. It occurs most often among school-aged children and preschoolers (including those attending child care centres), people living in institutional settings, and household members and caregivers of persons with pinworm infection. Cats and dogs are not involved in the spread of pinworms.

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How are pinworms spread?

Pinworm infection is spread by the transfer of infective pinworm eggs from the anus (bum) to someone’s mouth, either directly by hand or indirectly through contact with contaminated clothing, bedding, food, or other objects like toys. Pinworms are usually spread from child to child and from an infected child to their family members.

While an infected person sleeps, female pinworms leave the intestine through the anus (bum) and deposit their eggs on the surrounding skin. When the infected person scratches their anus (bum), the pinworm eggs may get onto their hands and under their nails and can be spread to others.

Since pinworm eggs can survive outside of the body for up to two weeks, contact with objects contaminated with pinworm eggs can cause infection as well.

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What are the symptoms?

Often there are no signs of infection. Itching and scratching around the anus (bum) is the most common symptom. In children, the itching may lead to disturbed sleep and irritability.

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How is it diagnosed?

The best way to see if a child has pinworms is to examine the anus (bum) for worms 2 to 3 hours after the child is asleep. In addition, your healthcare provider may recommend a “tape test” which involves placing sticky tape on the skin around the anus. The pinworm eggs are picked up by the tape and are identified under a microscope.

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How is it treated?

Most pinworm infections are mild and can be treated with oral medication. After the initial dose, the medication is repeated 2 weeks later to decrease the risk of re-infection. If a member of a family has pinworms, treatment of all household members may be considered. Infected people should shower every morning and thoroughly wash the anal area as this removes a large amount of the eggs.

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How are pinworms prevented?

 Thorough handwashing

  • Handwashing is the way to prevent the spread of infections.
  • The six steps to good hand washing are:
    1. Wet hands with warm running water
    2. Put liquid soap on hands
    3. Lather hands and scrub for 20 seconds
    4. Rinse under running water
    5. Dry your hands with paper towels
    6. Use the towel to turn off the taps



  1. Apply the hand rub to your hands. Use an amount about the size of a dime.
  2. Rub your hands together until the hand rub is gone. Hands will feel dry in about 15 seconds.

Keep nails trimmed

  • Keep nails trimmed short and discourage nail biting and thumb-sucking

Discourage scratching of the anal area (bum)

Shower everyday

  • Daily morning showering removes a large number of eggs. If showering is not possible (i.e. with young children), the infected person should bathe while standing to avoid getting contaminated bathwater in the mouth.

Do not share towels and washcloths

  • Towels and washcloths should not be shared and should be washed using the hot water cycle and dried on the hot cycle in the dryer.

Wash clothes and bedsheets

  • Underwear and pajamas should be changed and laundered daily. Bed sheets should be changed and laundered regularly especially after each treatment. The hot water cycle on the washing machine should be used to wash these items and a hot dryer should be used to dry them. Used bedding and clothing should be handled carefully since shaking can spread the eggs into the air.

Keep bedroom curtains and blinds open during the day

  • Eggs are sensitive to light, so open bedroom curtains and blinds during the day.

No exclusion from child care

  • Children with pinworms can continue to attend child care. .
  • Ensure children’s nails have been cleaned and trimmed.
Date of creation: June 9, 2015
Last modified on: January 11, 2016

Related Content



1Centers for Disease Control and Prevention (2013). Parasites- Enterobiasis (also known as Pinworm Infection). Retrieved May 12, 2015 from Retrieved from
2Heymann, D.L. (2015). Control of Communicable Diseases Manual (20th ed.) Washington, D.C.: American Public Health Association.