Threadworms, or pinworms as they are sometimes called, are parasites. A parasite is an organism which lives on or inside another organism. The threadworm parasite is called Enterobius vermicularis.Threadworms are tiny white worms which look like strands of thread. They measure approximately 1cm in length. They can be detected in the faeces, around the anus or on the buttocks. They can also cause itching around the anus especially at night, abdominal pain, sleep disturbances and a change in appetite.

Threadworms can affect people of all ages but they are particularly common in young children.

How Threadworms Are Spread

Threadworms live in the intestines of some human beings. During the night, females move towards the anus to lay their eggs. This egg laying process causes intense itching and subsequent scratching. As a result of scratching, eggs can be transferred to the hands or can become trapped under the fingernails. These eggs can then be passed on to other people by direct contact or they can be transferred to surfaces, objects, fabrics or food where they can be picked up by someone else. Hand to mouth contact and subsequent swallowing transfers the eggs to the intestine where they hatch. This allows the life cycle of the threadworm to begin again.

Avoiding Threadworms

  • Personal hygiene is very important, especially around the genital and anal areas. Change your underwear daily.Vacuum and dust your home regularly.Wash your hands thoroughly after going to the toilet and before eating or preparing food.Scrub your fingernails daily with a nailbrush to keep them clean. Keep bathrooms and toilets clean including flush handles, taps, door handles and light switches
  • Nail biting and thumb sucking should be discouraged, especially in children


Threadworm treatments, which destroy parasitic worms, are available over the counter at most pharmacies. They are known as 'anthelmintics' and they usually contain either piperazine or mebendazole. Piperazine treatments are available as powder sachets or liquid. Preparations containing mebendazole are available in chewable tablet form. If one member of a household has threadworms it is strongly recommended that the whole household be treated at the same time.Ointments such as petroleum jelly (also known as soft paraffin) can be applied to the anal area. This can help to relieve itching and to prevent the threadworms laying eggs during the night. The following precautions should be taken during infestation

  • Pyjamas should be worn in bed to prevent scratching during the night.Fingernails should be kept short.Bed linen should be changed regularly.Towels should not be shared.Hands should be kept clean and fingernails should be scrubbed. This is especially important first thing in a morning, before eating and after going to the toilet
  • Having a bath each morning will remove any eggs from around the anus

When To See A Doctor

Pregnant women, breast feeding mothers, babies and anyone suffering from kidney problems or epilepsy should see a doctor before using threadworm treatments.Women who also develop cystitis or notice unusual vaginal discharge should see a doctor. It could be that the threadworms have invaded the vagina or urethra (the tube which carries urine from the bladder) causing irritation.

Additional Information

A leaflet about cystitis is also available from this pharmacy.