Threadworms (pinworms)
Threadworms are tiny white worms that live in the bowel. They are the commonest worm infection in our part of the world, and it is usually a child who brings…
On this page
Threadworms are tiny white worms that live in the bowel. They are the commonest worm infection in our part of the world, and it is usually a child who brings them home from nursery or school. They cause nothing serious and usually leave nothing behind, but they have one tiresome habit: they come back easily. That is why the treatment is arranged in a way that surprises people at first — the whole household takes the medicine, and not just once.
How to tell it is them
The main sign is itching around the bottom that gets worse in the evening and at night. The female worm comes out to lay her eggs in the folds of skin, and she does it while the person is asleep and warm under the covers. Everything else follows from that.
- The child sleeps restlessly, tosses about, wakes up and is irritable during the day for no obvious reason.
- The skin around the anus is scratched, red and sometimes slightly cracked.
- Sometimes a child who stopped wetting the bed long ago starts again.
- Less often: poor appetite, tummy ache with no clear spot, grinding the teeth in sleep.
The worms themselves can be seen, and that is the most reliable way of settling the question. They look like short white threads up to a centimetre long, and they move slightly. Look two or three hours after the child has fallen asleep, with a torch, parting the buttocks. They also turn up on the bedding or in the stool.
If nothing has been seen but the suspicion remains, the doctor will suggest a simple test: in the morning, before washing and before going to the toilet, a piece of sticky tape is pressed against the skin around the anus for a couple of seconds and then taken to the laboratory. Sometimes the sample is collected on three consecutive mornings, because eggs are not laid every night. The ordinary stool test for worm eggs is unreliable here: the eggs stay on the skin rather than passing in the stool, so a negative result rules nothing out.
Where they come from and why they come back
The circle closes through the hands. At night the female lays her eggs around the anus, the skin itches, the person scratches in their sleep, and the eggs end up under the fingernails. From there they travel to everything that gets touched: clothes, towels, door handles, toys, crockery, food. One hand to the mouth later and it all starts again. A child can keep reinfecting themselves for weeks even with nobody else around.
Two facts explain almost everything about the treatment. First, the eggs survive about two weeks in the surroundings and drift about with the dust, so a single clean-up does not settle it. Second, if the eggs are in the house, everyone in the house has them — it is just that some people do not itch, carry them quietly and then pass them back to everyone else.
This is not a sign of a dirty home. Threadworms do perfectly well in immaculate houses and in children who are bathed twice a day. And one more thing: the dog or the cat has nothing to do with it. Threadworms pass only from person to person, and the pet does not need treating.
Treatment: the whole household, twice
The medicines are simple and dependable. They are anthelmintics — usually mebendazole, albendazole or pyrantel — as a chewable tablet or a liquid. Many are sold without a prescription, but choosing the medicine and working out the dose by weight is a job for the pharmacist or the doctor. There are two rules, and without them the treatment nearly always fails.
Everyone living in the house is treated, on the same day. Every adult and every child, including those with no symptoms at all. Treating only the person who itches is pointless: the others are carrying eggs and will hand the infection back within a week. If the child sleeps over at a grandparent's or spends weekends in a second household, the same has to be done there.
The dose is repeated after two weeks. This is the rule that gets broken most often. The medicine kills the adult worms but has no effect on the eggs. Eggs already swallowed hatch quite happily and grow into adult worms just as the second week ends. A second dose for the whole household closes that second cycle.
Have a separate conversation with a doctor if the person to be treated is pregnant or breastfeeding, or is a child under two. The decision is then made case by case: sometimes the medicine is postponed and strict hygiene is used instead for several weeks, which on its own is enough when it is done properly.
What to do at home for those two weeks
Hygiene works just as hard as the tablet here, because it breaks the chain that carries the eggs. The trick is to do the thorough part on the day the medicine is taken, and then keep up a few simple things for two weeks.
- On treatment day, wash the bedding, nightwear, towels and underwear of everyone in the house at a hot temperature. The soft toys the child sleeps with too.
- Do not shake the bedding before washing it. That simply scatters the eggs round the room. Fold it gently and take it straight to the machine.
- Wash yourself and the child every morning: most of the eggs collect on the skin overnight, and a morning shower takes them off before they reach the hands.
- Change underwear every morning. Wear close-fitting underwear at night, which makes it harder to scratch while asleep.
- Cut everyone's nails short and watch that children do not bite them or suck their fingers. Wash hands with soap and a nailbrush before eating and after the toilet.
- Dust with a damp cloth and vacuum daily, especially in the bedrooms; wash the toilet, taps and door handles with hot water.
- One towel each: put the shared ones away for these few weeks.
There is no need to stay away from nursery, school or work: threadworms are not a reason to keep anyone at home. It is worth telling the nursery if other children in the group have the same complaint.
In girls: itching and discharge
This is rarely spelt out, and it should be. In girls, threadworms often travel forwards from the anus into the vulva and the vagina. That brings itching and soreness in the genital area, redness, a scanty discharge and sometimes discomfort or frequent trips to pass urine.
Such a picture is easily taken for something else, and the child is put through investigations: swabs, urine tests, courses of antifungals and antibiotics that make no difference. Yet all it takes is to remember the night-time itching around the anus and do the sticky tape test. Where a girl has a stubborn vulvovaginitis that is treated again and again without result, threadworms must be ruled out.
When a doctor is needed
Threadworms are usually dealt with at home. But some situations need examining.
- Tummy pain with a temperature and vomiting, particularly if the pain has moved to the lower right side, is the picture of appendicitis and needs to be sorted out urgently, the same day. Do not put it down to worms.
- The itching has not gone after the whole household was treated properly, including the repeat dose. Then it probably is not threadworms: eczema, contact dermatitis from wipes and soaps, a fungal skin infection, an anal fissure, haemorrhoids and several skin conditions of the area all itch in a similar way. What is needed is a different diagnosis, not a third tablet.
- Worms of a different sort are visible in the stool: long, round, or flat segments. Those are not threadworms, and the treatment differs.
- The skin around the anus is badly scratched, weeping, crusted or spotted with pus: a bacterial infection has joined in.
- Weight loss, blood in the stool or a prolonged temperature: these have nothing to do with threadworms and need a cause found.
Online consultation
The subject is straightforward, which is exactly why the details go wrong so often — and because of the details the whole thing goes round in circles. At a remote appointment the doctor will help judge from your description and a photograph whether this looks like threadworms, explain how to do the sticky tape test properly and when to take it in, and choose the medicine with the age and weight of each member of the household in mind.
The second reason to get in touch is pregnancy, breastfeeding and children under two: the decision there is made separately and is better discussed in advance. And the third: if the itching persists after the whole household has genuinely been treated and given the repeat dose, a remote appointment is the place to work calmly through the other causes instead of buying yet another box of tablets.
Tummy pain with a temperature and vomiting, on the other hand, is not something to wait for an appointment with — that needs looking at in person the same day.
This material is for information only and does not replace medical advice.
Consult with a doctor about Threadworms (pinworms)
Discuss your symptoms and possible next steps with a doctor online.
Online doctors for Threadworms (pinworms)
Discuss your symptoms and possible next steps for Threadworms (pinworms) with a doctor online.
