A child who has started scratching a very specific itch, especially at night, has probably picked up threadworms. They are one of the most common parasitic infections in the UK, particularly in children aged 5 to 10, and they are so easy to clear that the treatment is a single pharmacy-counter tablet. The catch — and it is the catch that catches many families out — is that the whole household has to take the treatment at the same time.

This guide explains what threadworms are, what your pharmacist can dispense, and the hygiene routine that stops them returning.

What threadworms are

Threadworms, sometimes called pinworms, are small white parasitic worms around 5 to 13 millimetres long. According to the NHS, they live in the lower bowel of humans and at night the adult females crawl out to lay eggs on the skin around the anus. That is what causes the hallmark night-time itch.

The eggs are microscopic and highly transportable. A child scratches, picks up eggs under the fingernails, and transfers them to door handles, clothing, bedding and toys. Another family member picks them up, swallows them accidentally, and the cycle starts again. This is why treatment has to cover the whole household, not just the obviously affected child.

Threadworms are not dangerous. They do not cause weight loss, they do not travel to other organs, and they do not cause serious illness. But they are persistent, and they are a classic school-age embarrassment.

How to spot them

The key signs, per NICE:

• intense itching around the anus, typically worse at night
• disturbed sleep, irritability, or a child scratching in their sleep
• visible threadworms — tiny white, fast-moving threads — in the stools, on toilet paper, or on the skin around the anus

You can sometimes confirm threadworms with a night-time look. Using a torch, check the child's anal area an hour or two after they have fallen asleep. Worms are often visible on the skin at that point.

What the pharmacist will supply

For children aged 2 and over and most adults, the standard treatment is mebendazole 100 mg, sold as a single chewable tablet or sachet. Brand names include Ovex and Vermox.

The regimen is simple:

• one dose for everyone in the household on the same day
• a second dose, for everyone, two weeks later

The second dose is essential. Mebendazole kills adult worms but does not reliably kill eggs that may hatch after the first dose. Without the two-week follow-up, re-infection is almost guaranteed.

Your pharmacist will ask a few questions before supplying:

• Are you pregnant or breastfeeding? Mebendazole is not routinely used in the first trimester. Pregnant women are usually advised to rely on hygiene measures alone for six weeks.
• Is the child under two? Mebendazole is unlicensed below age two; the pharmacist will refer to a GP.
• Is anyone in the household on other treatment that might interact? Rare, but they will check.

The cost of a household pack is low — under £10 for a family-sized pack in most pharmacies — and you do not need a prescription.

The hygiene routine that matters

The tablet does the easy part. The hygiene routine does the rest, and the NHS recommends keeping it up for six weeks from the first dose:

• wash everyone's hands and scrub under the fingernails each morning and before every meal
• shower first thing in the morning, including the anal area, to remove eggs laid overnight
• change and hot-wash bedding, nightwear and towels on the day treatment starts
• vacuum and damp-dust the bedroom to pick up any shed eggs
• keep fingernails short; discourage nail-biting and thumb-sucking
• each family member should use their own towel

Miss any of these and the cycle can restart within a fortnight. Combine all of them and the infection clears for good.

What the pharmacist will refer

The pharmacist will suggest a GP consultation if:

• the affected person is under 2 years old
• the person is pregnant and the pharmacist is uncomfortable supplying the medicine for that stage
• symptoms have persisted after two full rounds of correctly administered mebendazole spaced 14 days apart
• there is abdominal pain, blood in the stool, or unexplained weight loss — all of which point to something other than threadworms
• the person is significantly immunocompromised

Most of these cases are uncommon. The overwhelming majority of threadworm cases are resolved at the pharmacy counter.

School and nursery

Children with threadworms do not need to be kept off school. The NHS advice is to treat immediately, reinforce the hygiene routine, and carry on. Teachers do not need to be informed unless the school has a specific policy, and there is no public health reporting requirement.

Myths worth dispelling

A few stubborn myths about threadworms that pharmacists still hear:

• Garlic and other home remedies do not reliably clear the infection. Mebendazole does.
• Only the obviously itching person needs treatment. No — everyone in the household needs treating on the same day.
• Deep cleaning the whole house is necessary. No — bedrooms and bathrooms are the key zones. Threadworm eggs do not survive long away from a host.
• Pets spread them. No — threadworms are a human-only parasite; the family dog or cat is not involved.

When to ask your pharmacist

Pop in if:

• you have spotted what look like threadworms on toilet paper
• a child in primary school has been scratching their bottom at night for several days
• you have treated once but symptoms have not fully cleared
• you are pregnant and not sure which hygiene steps are most important

To find a pharmacy near you, use the PharmSee directory.

Sources

• NHS — Threadworms (nhs.uk)
• NICE Clinical Knowledge Summary — Threadworm
• British National Formulary — Mebendazole prescribing information

PharmSee provides UK pharmacy consumer health guides based on NHS clinical guidance.