Pinworm (threadworm): symptoms, treatment and how to stop it coming back

The NHS says you can spot threadworms in your poo, where they look like pieces of white thread. You might also see them around your child's bottom. The worms usually come out at night while your child is sleeping. NICE Clinical Knowledge Summaries (CKS) says some people have no symptoms and only find out when small white thread-like worms are seen on the skin around the anus or in the stools.

• Extreme itching around the anus or vagina, particularly at night.

• Irritability and waking up during the night.

• Less commonly, weight loss, wetting the bed, or irritated skin around the anus.

• In girls and women, itching around the genital area (pruritus vulvae), according to NICE CKS.

The NHS says you can treat threadworms without seeing a GP. See a pharmacist if you think you or your child have them. You can buy a medicine called mebendazole from pharmacies, usually as a chewable tablet or liquid you swallow. The NHS says to treat everyone aged 2 years and over in your household, even if they do not have symptoms.

Tell the pharmacist if you need to treat a child younger than 2 years, or if you are pregnant or breastfeeding, because treatment might not be suitable and you may need to speak to a GP. If you cannot take medicine, you can treat threadworms by using hygiene methods for 6 weeks.

NICE CKS recommends mebendazole plus hygiene measures for adults and children over 6 months, notes that mebendazole is not licensed for children under 2 years, and recommends hygiene measures alone for 6 weeks for children aged 6 months and under, and for pregnant or breastfeeding women.

The NHS says medicine kills the threadworms but not the eggs, and eggs can live for up to 2 weeks outside the body. Do the following for 2 weeks if you are taking medicine, or for 6 weeks if you are not.

• Wash hands and scrub under fingernails, particularly before eating, after using the toilet or changing nappies.

• Encourage children to wash their hands regularly.

• Shower every morning, and rinse toothbrushes before using them.

• Keep fingernails short.

• Wash sleepwear, sheets, towels and soft toys at a hot temperature every day for several days after treatment.

• Disinfect kitchen and bathroom surfaces using hot water, and vacuum and dust with a damp cloth.

• Make sure everyone in the household wears underwear at night and changes it in the morning.

• Do not shake clothing or bedding, do not share towels or flannels, and do not bite nails or suck thumbs and fingers.

Yes. The NHS says threadworms spread when their eggs are swallowed. They lay eggs around the anus, which makes it itchy. The eggs get stuck on the fingers when you scratch, and can then pass onto anything you touch, including clothes, toys, toothbrushes, kitchen or bathroom surfaces, bedding and food. Eggs can pass to other people when they touch these surfaces and then touch their mouth.

NICE CKS describes threadworm as the commonest parasitic worm infestation in the UK, most often affecting children under 18, household contacts of infected children, and people living in institutions. It is not a sign of being unclean.

The NHS says larvae hatch from swallowed eggs in your gut and take 1 to 2 months to mature into threadworms. Children can get threadworms again after treatment if they get the eggs in their mouth, which is why handwashing matters.

NICE CKS says that if infestation recurs it is usually due to re-infection rather than treatment failure. If the diagnosis is certain, re-treatment of the person and household contacts with mebendazole is recommended, unless it is not suitable, and strict hygiene measures should be reinforced. If recurrences are frequent, NICE CKS advises seeking advice from a paediatrician or consultant in infectious diseases.

Often the diagnosis is made by seeing the worms. NICE CKS says that if the diagnosis is uncertain, an adhesive tape test for eggs may be useful: transparent tape is applied to the skin around the anus first thing in the morning and then examined under a microscope. Stool examination is not generally recommended.

Other causes of itching around the bottom or vulva include dermatitis, candida (thrush) infection, pubic lice and haemorrhoids, according to NICE CKS.

Threadworms are common in children and spread easily. The NHS says there is no need to stay off nursery, school or work if you or your child has them. Encouraging regular handwashing and keeping nails short matter more than time off.

The NHS says to see a pharmacist if you think you or your child have threadworms. Speak to a GP if treatment might not be suitable, for example for a child under 2 years or if you are pregnant or breastfeeding, or if symptoms keep returning despite treatment and hygiene steps. NICE CKS advises that other causes should be considered if symptoms continue after re-treatment.

Threadworm is usually dealt with through a community pharmacy, where the NHS says you can buy mebendazole without seeing a GP. A GP appointment is needed only if treatment is unsuitable or the problem keeps coming back. A private consultation is not normally needed.