Threadworms are known to cause intense itching around the anus. In girls, vaginal itching can also occur. The itching is particularly intense at night, when the female worms are active laying their eggs. This may cause you to experience a loss of sleep and make you irritable. In cases of very heavy infestation, or persistent infestations, threadworms can cause a loss of appetite, weight loss, insomnia and severe irritability. Threadworms do not always produce symptoms, which is why all members of your household must be treated, even if only one person develops the condition and experiences symptoms.

Threadworms are usually passed on through poor hygiene. If you have threadworms, the eggs are laid around your anus, along with the female worm's itchy mucus. If you scratch the affected itchy area, eggs may be transferred on to your hands. The eggs can then rub off on to other surfaces that can come into contact with people's mouths, such as children's toys, kitchen utensils, or toothbrushes. If the eggs are swallowed, the infestation cycle begins again. 

Children can also prolong their infestation by continually swallowing fresh eggs. As children regularly come into close contact with one another, and share toys, or hold hands while playing, re-infestation is often easy. Threadworms are commonly found in family groups, particularly those living in crowded conditions.

Person-to-person threadworm infestation can also occur through handling contaminated clothes, or bedding, or from touching contaminated surfaces, such as furniture and carpets. Eggs can survive on such surfaces for up to two weeks.

Threadworms only infest humans and cannot be caught from animals, such as dogs and cats. However, there is a small risk that threadworm can be caught from household pets if their fur becomes contaminated with eggs as a result of human contact. Only then could they continue to spread the parasite to humans by means of patting or stroking.

Threadworms are difficult to see because of their size and colour. The best time to try and see them is at night, when the females come out to lay their eggs. Sometimes, worms can be found in stools (faeces). The worms look like small pieces of white cotton thread, hence their name.

Your GP or nurse may take a moistened swab from around your anus to pick up eggs. The sample can then be sent to a laboratory for testing.

Treatment for threadworms is aimed at getting rid of the parasites and preventing re-infestation. To successfully treat threadworms you can either follow strict hygiene methods (as outlined below), or take medication such as Ovex Suspension or Ovex Tabs. However, when taking medication, you should also ensure strict hygiene methods to prevent re-infestation.

Hygiene
Sensible hygiene measures can be used to clear up a threadworm infection, but also to reduce your chances of re-infestation. The life span of the threadworms is approximately six weeks so these hygiene methods should be followed for this period. These include:
- keeping finger nails short,
- discouraging nail biting or finger sucking - in particular, you should make sure that children do not suck their thumb,
- frequently washing hands, and scrubbing under finger nails, particularly before eating and after visiting the toilet,
- wearing close-fitting underwear at night, making sure to change them every morning,
- wearing cotton gloves at night as this may help prevent scratching during sleep,
- having a bath, or shower, and making sure that you clean around the anus and vagina each morning, to remove any eggs laid during the night,
- making sure everyone has their own face flannel and towel avoid using communal (shared) towels,
- not eating food in the bedroom, as eggs can be shaken off bedclothes and survive in dust, and
- vacuuming regularly and thoroughly.

Medication
Medicines can also be used to remove threadworms. The most common medications used are:
- Mebendazole - this kills the threadworms, usually with only one dose (100mg), and is the preferred treatment for anyone over two years of age. If re-infestation does occur, a repeated dose can be prescribed.
- Piperazine paralyses the worms until they are pushed naturally out of the bowel. Piperazine can be used in children aged from three months to two years of age, but needs to be taken in two doses (2.5ml each), two weeks apart.

Mebendazole and piperazine do not kill the eggs produced by threadworms, so strict hygiene measures should still be followed for two weeks after treatment. All members of your family, or household, need to be treated at the same time to avoid re-infestation, even if only one person displays symptoms. These medications should not be used in babies who are less than three months old.

If the infestation persists after using medication, see your GP who is likely to recommend that you begin a second course of medication. The whole family should be included in this treatment, and additional hygiene measures should be practised. These include:
- washing sleepwear, bed linen, towels, and cuddly toys - this can be done at normal temperatures but make sure that the washing is well rinsed,
- thoroughly vacuuming and dusting the whole house paying particular attention to the bedrooms,
- carefully clean the bathroom by 'damp-dusting' surfaces, and washing the cloth frequently in hot water, and
- keeping toothbrushes in a closed cupboard, rinsing them well before use.

During pregnancy
Medication for threadworm is not usually suitable during pregnancy and while breastfeeding. Only in the second or third trimester (weeks 14-26 and week 27 onwards) of pregnancy can medication be used. Mebendazole is often prescribed. Mebendazole or piperazine should never be taken during the first trimester of pregnancy. See your GP if you are unsure.

Threadworms can cause intense itching around the anus and vagina. Continual scratching can cause your skin to become inflamed. In rare cases, if the skin is broken, this may lead to another infection. See your GP or call NHS Direct on 0845 4647 for further advice on treatment options available to you.
Threadworm infestation outside of the intestine is very rare. It has been known to occur in the vagina, the uterus (womb), the pelvic peritoneum (lining on the inside of the abdomen), the abdominal cavity (stomach area), the liver, and even the lungs.

Re-infestation is common if threadworm is left untreated, with the possibility that it will become a persistent (ongoing) problem.

Threadworms can be prevented by ensuring that your standards of hygiene are high (see the 'treatment' section). Children in particular should be taught to wash their hands regularly, especially after going to the toilet and before meals. Also try to ensure that your kitchen and bathroom surfaces are regularly cleaned.

Children with threadworms do not need to stay away from school. However, schools and nurseries should be encouraged to take hygiene measures. The advice given by the Health Protection Agency (HPA) is that children do not need to be kept off school because the risk of spreading threadworms is relatively low, and that it is generally considered to be a mild illness in childhood.

Encouraging children not to scratch the affected area around their anus will help prevent re-infestation, and will avoid any secondary infections occurring as a result of scratching. However, because the itching frequently occurs at night, it may be possible to scratch the area while asleep without realising.