Download now


Threadworms are small worms that cause itching around the anus. They’re common in children and spread when threadworm eggs are swallowed. Good hygiene can help break the cycle of infections. Otherwise, there’s medical treatment that can help.

What are threadworms?

Threadworms, also known as pinworms, affect around 10–30% of children at some point. Adults can also get them. While it’s unpleasant, threadworms don’t cause serious problems.

Threadworm eggs can be found in dust, on textiles and in a pet’s fur. The eggs are small and hard to see, though sometimes tiny white specks are visible.

Adult threadworms are visible with the naked eye, and you can sometimes see them in your poo. They are yellowy-white, thin and about 5–13 millimetres long. The number can vary throughout an infection, from just a few to several hundred.

Symptoms of threadworm infections

There aren’t always visible signs of threadworm infection, and not everyone gets symptoms. If you do, they usually start with itching and redness around the anus where the worms lay their eggs. The itching is often worse at night when you’re warm and the worms are most active. Because the vulva, or area around the vagina, is close to the anus, threadworms may also cause itching and swelling there.

Children with threadworms often have trouble sleeping. Very small children might show their discomfort by kicking or sliding around on their bottoms.

Common symptoms:

  • Itching and redness around the anus
  • Itching and swelling around the vaginal opening
  • Small, yellow-white worms around the anus or in poo

Other possible explanations

Itching around the anus is not always caused by threadworms. There are also other types of worm infections, like roundworm, human whipworm or hookworm.

If you haven’t spotted any worms, things like eczema, fungal infections, anal fissures or piles can cause some similar symptoms.

What causes threadworms?

Threadworms spread through their eggs. Eggs can stick to fingers, objects, clothing, sheets, towels, dust or in the fur of pets. If they get into the mouth, they become worms.

The lifecycle of a threadworm from egg to adult worm can take over a month. The eggs can survive outside the body for several weeks. When they get into the mouth, it takes 3–4 weeks until the adult worms hatch in the gut. They lay new eggs around the anus before they die.

Children with threadworms can infect themselves again if they scratch their bottom and then put their fingers in their mouth.

Treatment for threadworms

Threadworms are usually seen around the anus, but if you’re unsure, doing a 'tape test' can help confirm the diagnosis. Stick a piece of clear tape around the anus first thing in the morning when you wake up, then gently remove it and check for eggs.

The first step to treating threadworms is diligent hygiene. The goal is to wash the eggs off your hands and around the mouth to avoid reinfection. Handwashing is key, but keeping your home clean and washing your clothes and sheets is just as important.

If someone in your family is already infected or there’s an outbreak of threadworm infections at school, medical treatment may be recommended. The medication works against worms and larvae after a few days, but the eggs can survive for another 2-3 weeks, so the medicine needs to be repeated again after 2 weeks.

Since many things can cause anal itching, you should only be treated with medications against threadworm if you have spotted worms, or if a test confirms the presence of eggs or worms.

What can I do myself?

Threadworms can be prevented and treated by washing your hands often and practising good hygiene at home. Wash towels, bedlinen and underwear at a minimum of 60 degrees C, as the eggs can survive at lower temperatures.

How to lower the risk of infection:

  • Wash your hands often with liquid soap, and dry them with paper towels
  • Change your underwear and pyjama trousers every day
  • Change your bed linen and towels every day
  • Change and wash your clothes as soon as you come home
  • Prevent dust by vacuuming and cleaning, especially in the bathroom and bedroom
  • Clean the toilets and sinks every day
  • Wash textiles and cuddly toys at 60 degrees
  • Bathe your pets’ fur to wash away any eggs

Children with threadworms don’t need to be kept home from school, but some schools have their own guidelines. Always tell the school staff if your child has threadworm.

When should I seek medical help?

If you or your child have threadworms that won’t go away even with diligent hygiene, speak to a doctor. The same applies for recurring threadworm infections, or if you have seen any other kinds of worms.

You should also see a doctor if you see slime or blood in poo, even if you don’t have other symptoms of threadworm.

How Livi can help

Livi can help treat threadworms. A doctor will make an individual assessment based on your symptoms. You may then be given a prescription for treatment or referred for specialist care.

Remember that if the appointment is for your child, they must be present at the appointment.

Reviewed by:

Kristina Bergstrand

Specialist in general medicine


Sign up to our newsletter for the latest health information and GP-approved lifestyle tips, to help you live your healthiest life every day.