Also called pinworms

Having threadworms is common in childhood, but anyone of any age can be affected. Threadworms are not harmful, but they can be itchy and annoying or they can go unnoticed in some people.

Threadworms are small, thin, white worms between 2mm and 13mm long, that look like cotton threads and live in your bowel. Strict hygiene measures can help clear up a threadworm infection and reduce the likelihood of reinfection.

To treat threadworms successfully, all household members must be treated, even if they don't have any symptoms.

How do you get threadworms?

Threadworms are spread from human to human. They are not carried by animals so don't come from pets. Threadworms are spread easily within families, creches and daycare centres, schools, and camps. If one person in your family has threadworms, others probably do too.

  • Most people get threadworms by swallowing the worm's eggs. Threadworms leave your gut at night and lay eggs on the skin around your anus (bottom). The eggs can get onto your hands or under your fingernails through scratching the itchy area or because of poor handwashing after using the toilet.
  • You can pass them on to an uninfected person, for example through food handling.
  • Threadworm eggs can also get onto carpets, bed linen, towels, flannels and into household dust and in this way, they are passed from person to person.
  • It may be between 2 and 6 weeks after contact with a source of infection before the life cycle is complete and eggs are laid in the newly infected person.

What are the signs of threadworms? 

The most common sign of threadworms is itching around the anus (bottom), which is worse at night. This is because the worms are most active at night.  In some instances, the worms can be seen in the stool (poo) or on toilet paper. Other signs include bedwetting, restless sleep, loss of appetite, and irritability. Many people with a threadworm infection have no symptoms.

How is threadworm infection diagnosed?

The most obvious way an infection is diagnosed is if the threadworms can be seen in the stool (poo) or on toilet paper. But, if this is not the case your doctor may ask you to do a sticky tape test to confirm the presence of threadworms. To do this you press some clear see-through tape on to the skin around your anus (bottom) first thing in the morning, before wiping or bathing. You then place the tape on a glass slide or put it in a specimen container. The tape is then sent to the laboratory to be looked at under a microscope to see if any threadworm eggs are stuck to it.

How is a threadworm infection treated?

In most cases, a threadworm infection can be treated with strict hygiene measures. This also reduces the likelihood of reinfection. Medication to treat a threadworm infection can be bought over the counter from your local pharmacy or prescribed by your GP.

Hygiene measures

It's important to limit your chances of getting threadworms and of spreading them to others.

  • Wash your hands carefully and often.
  • Avoid scratching around your anus.
  • Keep your fingernails short.
  • Wash your clothes and bedding regularly.
  • Bathe and change your underwear every day.
  • Avoid sharing a bathtub or sharing face cloths.
  • Vacuum your carpets often.


You can buy worm medication such as mebendazole from your pharmacy. This medication will kill the worms in your gut but will not kill the eggs that have been laid around your anus (bottom). Eggs can survive for up to 2 weeks outside your body, on underwear or bedding, and in dust, so proper hygiene measures are important.

  • All household members, including adults and those without symptoms, should be treated with worm medicine at the same time.
  • It is recommended you take 2 doses of mebendazole – one dose initially and another dose 2 weeks later.
  • Read more about mebendazole.

When to see your GP?

In most cases, you won’t need to see your GP. However, if you are pregnant or breastfeeding and have threadworms, or if your child is under 2 years old and has threadworms, then you should see your GP. This is because the recommended treatment in these circumstances is usually isn't the same as different from that recommended for most other people.

Learn more

Threadworms Regional Public Health, Greater Wellington Region


Pinworms DermNet, New Zealand

Credits: Health Navigator Editorial Team. Reviewed By: Sandra Ponen, Pharmacist Last reviewed: 21 Aug 2017