What are they? What are the symptoms? What are the treatments?

What are threadworms?

A threadworm is a type of small parasitic worm that can infest human intestines, although they are not harmful. They're so called because they resemble fine pieces of white thread. They're most common in children, and it's thought that up to four out of 10 under-10s will get threadworms at some point.

Threadworm eggs live in all sorts of places, from house dust to clothing, towels and bed linen. From here they can easily make their way into a child's mouth, through poor hand washing or during their sleep if they inadvertently touch their mouth. Once inside the intestine, the eggs hatch and they multiply. 

Threadworms 474

The female threadworm lays eggs around the anus of the infested person and this causes a lot of troublesome itching, especially at night. If that person scratches their bottom and doesn't wash their hands and clean under their fingernails, the eggs - which are microscopically small – can be transmitted to hard surfaces, bedding, towels and food. 

From here, it's very easy for another person to ingest them by coming into contact with them and putting their hands to their mouth, or eating food containing threadworm eggs, so the cycle can continue.

Threadworm eggs can live for three weeks before they hatch. Two weeks after hatching they reach maturity and begin to reproduce. Often, a whole household can become infested with threadworms and six weeks of treatment – the lifespan of a threadworm – will need to be undergone before all family members are clear.

Animals can't catch or pass on threadworms unless there are eggs in their fur that get transferred to human hands. Humans are thought to be the only host for threadworms.

What are the symptoms of Threadworms?

The only symptom is usually intense itching around the anus and, in girls, the vagina, typically at night time. The best way to diagnose the problem is to check the anus of the affected person by using a torch at night. The adult female worm can be 8-13mm long, and the male 2-5mm long.

What are the treatments and remedies of Threadworms?

There are treatments available on prescription or over the counter, and these kill the threadworms, but not their eggs. The medication should be taken by all members of an infested household. Because the eggs won't have been killed, it's really important for everyone concerned to be scrupulous about hygiene for at least six weeks to prevent the infestation from spreading or returning.

Expectant mums shouldn't take medication for threadworms in the first trimester of pregnancy, but if it becomes necessary in the second or third, there is a drug that can be prescribed.

Babies under the age of three months can't take the medication either, but hygiene measures are often enough amongst this age group as they can't access their own bottoms.

This guide 

The information in this Bounty A-Z of Family Health is not a substitute for an examination, diagnosis or treatment by a doctor, midwife, health visitor or any other qualified health professional. If in doubt, always speak to a doctor.

Bounty will not be held responsible or liable for any injury, loss, damage, or illness, however this occurs or appears, after using the information given on this website and in particular the A-Z of Family Health.

Further help

For health advice and information 24 hours a day, 365 days a year, the NHS offers call and web services. You can also visit NHS websites for services, health information and health news at nhs.uk 

  • England – call 111 from any landline or mobile phone free of charge, or visit nhs.uk 
  • Scotland – call 111 from any landline or mobile phone free of charge, or visit nhs24.com 
  • Wales – call 0845 4647 , or visit nhsdirect.wales.nhs.uk 
  • Northern Ireland – visit hscni.net