Updated 2010-10-11

Threadworm is…

…an infection that occurs when threadworm parasites infest human intestines after threadworm eggs—which are not visible to the naked eye—are swallowed. It is also known as pinworm.

Symptoms

The main symptom of threadworm is itching in the anal area, which varies from mild to acute pain and occurs mainly at night. People with threadworm infection often do not have any symptoms. Sometimes threadworms—which have a white, thread-like appearance—are seen on a patient’s skin or in their stools. Other general symptoms may include insomnia and restlessness and some children may have a loss of appetite, lose weight and be irritable.

Complications

Vulvitis can be caused by threadworms entering the vulva causing itching and discharge. Other complications are rare.

Ways to catch threadworm

Threadworms pass through the intestines when the eggs have been swallowed and exit the body through the anal region, where they lay more eggs on the skin. This usually happens at night when the infected person is asleep and causes itching in the anal area. Scratching the area can cause the fingernails to become contaminated and the eggs can then re-enter the body through the mouth. Eggs can remain infectious for up to two weeks in house dust, clothing and bed linen and people can be infected from soiled bed linen, clothes or breathing in contaminated dust.

People most at risk

Threadworm is the most common parasitic infection in Europe. It is most commonly found in children aged 5–10 years living in overcrowded conditions or institutions, but adults can also be affected. Poor personal hygiene, finger sucking and nail biting can all increase the risk of getting threadworm.

Diagnosis

Diagnosis is usually done by detecting the threadworm eggs: adhesive tape may be applied to the anal area first thing in the morning before bathing and then examined under a microscope to detect the eggs.

Treatment

Threadworm can be treated using antihelminthic drugs, which destroy parasitic worms. It is recommended that all members of a family are treated at the same time to reduce the risk of re-infection.

How to avoid getting threadworm

The drugs used to treat threadworm will only destroy the parasites and do not have any effect on the eggs, so strict hygiene for at least six weeks is important to stop re-infection by transferring the eggs to the mouth. This includes the following measures: careful hand washing before eating and after using the toilet; keeping fingernails short and avoiding nail biting or finger sucking; bathing or showering every morning to remove eggs laid at night; avoiding sharing towels or flannels; wearing underwear at night to discourage night time scratching; and changing bed linen frequently.

What to do if you have threadworm

Children do not need to be kept away from schools or daycare facilities because threadworms can often be passed on by people who are not symptomatic and generally only cause mild illness in childhood.

Note: The information contained in this factsheet is intended for the purpose of general information and should not be used as a substitute for the individual expertise and judgement of healthcare professionals.