What are threadworms?

Threadworms are tiny, very thin white worms up to 13 millimetres long that live in the intestine and around the anus (bottom). They are also called pinworms. They look like small threads of white cotton, hence their name. They are widespread in Australia. Although people of any age can get them, children are the most susceptible.

Where do threadworms come from?

Threadworms produce large numbers of microscopic eggs. These eggs are present in house dust and stick to clothes, carpets and bedding. They can also be transmitted through contact with a person who is already infected with worms. It is very easy for people to ingest the eggs because the worms produce so many of them and they are so small.

After the eggs have been ingested they pass into a person’s small intestine (bowel) where they hatch and mature. A few weeks after hatching out these worms can reproduce — usually about a month later. When the worms are fully grown, the female comes out onto the skin around the bottom at night and lays eggs. At this time, symptoms may develop, including the classic one of a severe ‘itchy bottom’. The worms can also often be seen on bowel movements or around the anus especially at night.

Some children have no symptoms at all, but some of the other signs of threadworm infection your child may show are:

  • tiredness;
  • disturbed sleep;
  • teeth grinding;
  • bedwetting;
  • nose rubbing; and
  • loss of appetite.

Threadworms do not go away by themselves, and people do not build up immunity to them, so they must be treated in order to eradicate them totally from the body.

How serious are threadworms?

They are more embarrassing than anything else, because they can cause an irresistible urge to scratch the bottom. They are generally harmless and don’t cause long-term damage. However, scratching can aggravate the problem and make it more difficult to treat.

Diagnosis and treatment

If you think your child has worms you should see your doctor, who may do tests to diagnose the condition and identify the type of worm involved.

Fortunately treatment for threadworms is very easy. Usually only one or 2 doses of a medication is needed to kill the infestation — once initially and then a second dose repeated 2 weeks after the initial dose if required.

Many anti-worm preparations, for example pyrantel (brand names include Anthel and Combantrin) and mebendazole (e.g. Vermox) can be bought over-the-counter at pharmacies, but some are only available on prescription, such as albendazole (Zentel). Some anti-worm medicines are unsuitable for pregnant women or children aged less than 12-24 months. Suspensions are available for children not old enough to take tablets. Your doctor will advise you on the most appropriate treatment.

Zinc cream or mild antiseptic cream used around the bottom at night and in the morning can help with itching.

Doctors advise treating the whole family if one member has worms, even if others have no symptoms. This is because the worms spread very easily and re-infection is common. If multiple children from a school class or friendship group are infected it is a good idea to treat everyone simultaneously.


Re-infection can occur even if a child has been treated very recently. This is because the worms lay eggs around the bottom, causing irritation and prompting the child to scratch. As a result of this, or if the child doesn’t wash his or her hands after going to the toilet, the child will get the worm eggs lodged under the fingernails, and then they may be carried to the mouth. Then the eggs get back into the child's intestine, hatch out and a new batch of worms is produced, thus starting the whole cycle again.

So, to prevent re-infection, make sure that:

  • children’s fingernails are clipped short;
  • their hands and nails are scrubbed before meals;
  • they wash their hands after going to the toilet;
  • bed linen and towels are washed and changed frequently;
  • you disinfect the toilet seat daily for a week after treatment; and
  • the children wear underpants at night.

Do threadworms affect animals?

No. Threadworms are a different type of worm from those that animals get. Threadworms can’t be transmitted between people and animals. However, it is important to ‘worm’ your pets regularly for their own health and also because children can get other types of worms from animals.

Last Reviewed: 13/05/2009