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Digestive health centre


What are threadworms?

Threadworms are small, white worms that infect the intestines of humans. They are between 2 millimetres to 13 millimetres long and look like a piece of cotton thread, hence the name. They are sometimes known as pinworms.

They are the most common worm parasite in children in the UK, affecting up to half of all under 10s. The risk of other family members getting them from an infected child is as high as 75%.

How do you get threadworms?

Children touch and then swallow the tiny worm eggs without realising it. The worms hatch in the gut, then wriggle out of a person’s bottom at night to lay more eggs.

The female threadworm lays tiny eggs around the anus and vagina (in females). It also secretes mucus that makes you scratch the area.

The eggs get stuck to your fingers or under your nails and then they can be transferred to the mouth for the whole process to start again. Or you could transfer the eggs to someone else by touching them or touching a surface, which they then touch.

They are passed on by poor hygiene, not washing your hands after going to the toilet or coming into contact with objects contaminated by the worm’s eggs. Dirty fingers are put into the mouth; then the eggs grow into worms in the intestines.

Sometimes you don’t even know you have them but the main symptom is an itchy bottom which is worse at night and can disturb sleep.

The eggs can by transferred from your bottom to underwear, bed sheets towels and carpet.

Once the eggs are on your hands they can be transferred to anything you touch like children’s toys, a toothbrush, furniture or a kitchen worktop.

Threadworm eggs can survive on surfaces for up to three weeks. It is also possible to breathe in the eggs and then swallow them. The eggs are so small that they can become airborne, for example, if you shake a towel or bed sheet that has eggs on it.

Humans are thought to be the only host for threadworms. Animals cannot catch or pass on threadworms, unless the eggs are transported on the animal’s fur after human contact.

How do you get rid of threadworms?

If one person in a family has them, others may well have them too. So it’s best to treat the whole household to prevent re-infection.

You get rid of them by following strict hygiene measures for up to six weeks.

You can also get treatments from your GP or over the counter from pharmacies.

The most common medications that are used to treat threadworm infections are mebendazole and piperazine.

Treatment may not be suitable for everyone and you should always follow the manufacturer’s instructions.

Treatment alone does not kill threadworm eggs - good hygiene is the only way to prevent eggs from spreading and causing another infection.

WebMD Medical Reference

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