How can I check for pinworms?

The simplest way is to look at the skin around your child's anus with a torch an hour or two after they fall asleep, when the worms come out to lay eggs; they look like small, moving white threads. You may also see them on the surface of the stool. If nothing is visible but symptoms suggest worms, your doctor can arrange a sticky tape test.

Why does the whole family need treatment?

Pinworm eggs spread very easily and many infected people have no symptoms, so if only the itchy child is treated, others in the household can quietly pass the infection straight back. Treating everyone on the same day, combined with two weeks of hygiene measures, breaks the cycle. Pets do not need treating, as pinworms only infect humans.

Why do pinworms keep coming back?

Reinfection is the usual reason. The medication kills the worms but not the eggs, which can survive on surfaces, bedding, and under fingernails for up to two to three weeks. If hygiene measures slip, eggs are swallowed and the infection restarts. Repeating the dose after two weeks and being strict about hand washing, nail cutting, and laundry is the key to getting rid of them for good.

InfectiousICD-10: B80Very common worldwide, especially among children of nursery and primary school age and their households

Pinworms

Also known as: Threadworms, Enterobiasis, Seatworms

Pinworms, also called threadworms, are tiny white worms about the size of a staple that live in the human bowel. They are the most common worm infection in many countries and particularly affect children of school and nursery age, along with their families. The female worms crawl out of the anus at night to lay thousands of microscopic eggs on the surrounding skin, which causes intense itching. Scratching transfers eggs to the fingers and under the nails, from where they spread to surfaces, food, and other people and are swallowed, continuing the cycle. Pinworms are unpleasant but harmless, do not indicate poor hygiene, and are easily treated with medication combined with strict hygiene measures to stop reinfection.

At a Glance

Common symptoms: Itching around the anus, worst at night, and in girls sometimes around the vagina, Disturbed sleep, restlessness, or irritability, Small white thread-like worms visible around the anus, on the stool, or on underwear or bedding, especially at night
Main treatments: A single dose of mebendazole (or pyrantel in some countries), usually repeated after two weeks to kill newly hatched worms, Treating everyone in the household at the same time, including those without symptoms, Strict hygiene for at least two weeks alongside medication: hand washing, nail cutting, morning showers, and daily changes of underwear and nightwear
Category: Infectious · Very common worldwide, especially among children of nursery and primary school age and their households
See a doctor if: You see worms, or itching persists after a full course of treatment and hygiene measures

Symptoms

Itching around the anus, worst at night, and in girls sometimes around the vagina

Disturbed sleep, restlessness, or irritability

Small white thread-like worms visible around the anus, on the stool, or on underwear or bedding, especially at night

Redness or irritation from scratching

Reduced appetite or mild tummy discomfort in some children

Many infected people have no symptoms at all

Causes

Swallowing pinworm eggs from contaminated fingers, surfaces, toys, food, or bedding
Scratching the itchy anal area and transferring eggs to the mouth (self-reinfection)
Breathing in and swallowing eggs that have become airborne from shaken bedding or clothing
Close contact in households, nurseries, and schools

Risk Factors

Age 5 to 10 years
Having a child in nursery or primary school
Living in a crowded household or institution
Nail biting, thumb sucking, and infrequent hand washing
Having a family member or close contact with pinworms

Diagnosis

Seeing the worms around the anus at night or on the stool, which is often enough to diagnose
The 'tape test': pressing clear sticky tape against the skin around the anus first thing in the morning and having it examined under a microscope for eggs
Stool tests are not useful, as the eggs are laid on the skin rather than passed in stool

Treatment

A single dose of mebendazole (or pyrantel in some countries), usually repeated after two weeks to kill newly hatched worms
Treating everyone in the household at the same time, including those without symptoms
Strict hygiene for at least two weeks alongside medication: hand washing, nail cutting, morning showers, and daily changes of underwear and nightwear
Washing bedding, towels, and nightwear in hot water, and vacuuming and damp-dusting bedrooms
Hygiene measures alone for six weeks as an alternative for pregnant women and children under two, in whom medication may not be advised; a doctor can give specific guidance
Supportive: a soothing cream for the irritated skin, and cotton underwear or close-fitting pyjamas at night to limit scratching

Prevention

Wash hands thoroughly after using the toilet, before eating, and after handling pets or playing outside
Keep fingernails short and discourage nail biting and thumb sucking
Shower or wash the bottom first thing each morning to remove eggs laid overnight
Change underwear daily and avoid shaking bedding, which spreads eggs into the air
Avoid sharing towels and flannels
Clean bathroom surfaces, door handles, and toys regularly

When to See a Doctor

You see worms, or itching persists after a full course of treatment and hygiene measures
Infection in a child under 2, or during pregnancy or breastfeeding, where advice on treatment is needed
Severe irritation, skin infection from scratching, or vaginal symptoms in girls
Abdominal pain, weight loss, or blood in the stool, which are not typical of pinworms and need assessment

Frequently Asked Questions

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Vaginitis

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