Threadworms (pinworms)

by | Kids and Teens Health

Threadworms (pinworms)

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. Threadworms (Enterobius vermicularis) are the only type of worm infection commonly seen in Australia, and they are widespread. Although people of any age can get them, children are the most susceptible.

Where do threadworms come from?

Threadworms have only one host – humans. The adult threadworms live in the colon and rectum. The females produce large numbers of microscopic eggs, which they lay around the anus at night.

The eggs can fall off the skin around the anus and stick to clothes, carpets and bedding, becoming airborne when these items are changed or disturbed, and then they may settle into house dust.

The worms are caught by accidentally ingesting the eggs, which then hatch and infect the intestine. They can also be transmitted through direct 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.

Self re-infection is also common and results from the microscopic eggs sticking to the fingers or lodging under the fingernails after scratching the anal area, and then being re-ingested. Also, because the eggs may survive for several weeks, infection may be through contact with contaminated objects, such as bedding or clothing.

After the eggs have been ingested, they pass into a person’s small intestine (bowel) where they hatch into larvae which then migrate to the colon 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.

Threadworm symptoms

Threadworm symptoms usually have a sudden onset, often at night. The classic symptom is a severe ‘itchy bottom’. The worms can also often be seen on bowel movements or around the anus, especially at night. The area around the anus may be red and have scratch marks.

Some people with mild infections have no symptoms at all. Children may show other signs of threadworm infection such as:

  • tiredness;
  • disturbed sleep;
  • irritability
  • teeth grinding;
  • bedwetting; 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.


If you think you or your child has worms, you should see your doctor, who may do tests to diagnose the condition and identify the type of worm involved. The doctor may do a ‘sticky tape test’, which involves gently pressing a clear piece of adhesive against the anal skin, then examining the tape under a microscope to look for eggs. This is best done first thing in the morning before any eggs are washed or wiped away.

If another type of worm is suspected, you may need to give a stool sample for testing.

Treatment for threadworms

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

Many anti-worm preparations, for example pyrantel (e.g. brand names Anthel, Combantrin and Early Bird) and mebendazole (e.g. Combantrin-1 with Mebendazole) can be bought over-the-counter at pharmacies. However, 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 at the same time.


Re-infection can occur even if you or your child has been treated very recently. This is because the worms lay eggs around the bottom, causing irritation and prompting scratching. As a result of this, or if you or your child don’t wash your hands after going to the toilet, you will get the worm eggs lodged under the fingernails, and then they may be carried to your mouth. Then the eggs get back into the 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:

  • fingernails, especially children’s are clipped short;
  • hands and underneath the nails are scrubbed before meals;
  • you wash your hands thoroughly before eating and after going to the toilet;
  • bed linen and towels are washed in hot water and changed frequently;
  • hard surfaces are washed regularly;
  • vacuum carpets and furniture to remove any eggs;
  • bath or shower daily in the morning, to help wash the eggs away;
  • you disinfect the toilet seat daily for a week after treatment; and
  • children wear underpants and pyjamas at night, to help prevent anus-to-mouth transfer.

Do threadworms affect animals?

No. Threadworms are a different type of worm from those that animals get. You can’t catch threadworms from your pet. 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.

Can my child go to school or childcare with threadworms?

Your child can go to school or childcare if they have been treated for threadworms. If they are having loose bowel motions, they should be kept at home.

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