Pinworms (threadworms): Symptoms, causes, and treatments

The pinworm, also known as threadworm, is a very common intestinal parasite. The medical condition associated with pinworm infestation is known as enterobiasis.

According to the Centers for Disease Control and Prevention (CDC), pinworms are the most common type of worm infection in the United States.

They are parasites, meaning that they use the human body to survive and reproduce. Human pinworms cannot infect any other animals.

Adult worms are just 0.2 to 0.4 inches or 5 to 10 millimeters (mm) in length, about the size of a staple. They are white or cream colored and look like small pieces of thread. Pinworms can live for up to 6 weeks.

This MNT Knowledge Center article will explore the causes, symptoms, and treatments in more detail.

Fast facts:

The worms mature in the intestine and then move through the digestive system to lay eggs, at night, in the anal area.

The itchiness tends to be worse or more noticeable at night, and can sometimes wake a person with pinworms.

A pinworm can lay thousands of microscopic eggs.

Pinworm eggs are not visible to the naked eye.


woman having trouble sleeping
Sleep disturbance is a common symptom of pinworms (threadworms).

If an individual only has a small number of adult worms, the symptoms will be mild, or there may be no symptoms at all. Symptoms are worse with heavy or moderate infections.

About 4 weeks after ingesting pinworm eggs, the mature females make their way out from the intestine to the anal area, where eggs are laid in a jelly-like substance.

It is this substance that is believed to cause a person to itch, which usually happens at night. During the maturing and reproduction stages, a person with pinworms may experience:

disturbed sleep

itching of the anal area, which may sometimes be intense, especially at night when the female worms are laying eggs

mild nausea

Individuals with severe infection may experience:

loss of appetite

severe irritability

intermittent abdominal pain

sleeping difficulties

weight loss

If somebody is found to have an infection, all other members of the household should be treated too, even if they have no symptoms.

vacuum cleaning a carpet
Hygiene and cleaning is an effective method for removing pinworms in a home.

Strict hygiene measures can remedy pinworm infection and significantly reduce the risk of re-infection.

The worm has a life span of about 6 weeks, so any hygiene measures taken need to last at least that long.

Everyone in a household with pinworms must adhere to the following:

Wash all bed linen, bedclothes, and cuddly toys. A normal washing temperature is acceptable, but it needs to be well-rinsed.

Vacuum the home thoroughly, especially the bedrooms. Vacuuming needs to be regular and thorough throughout the 6-week period.

Damp-dust surfaces in the kitchen and bathroom, washing the cloth often in hot water regularly.

Do not shake things that may have eggs on them, such as clothing, pajamas, bed linen, or towels.

Do not eat in the bedroom. There is a risk of swallowing eggs that have shaken off the bedclothes.

Make sure the fingernails of every member of the household are cut short.

Refrain from nail biting and finger sucking. This may not be easy if there are small children in the house.

Wash your hands thoroughly and frequently, and scrub under the fingernails. Before eating, after going to the toilet, and after changing diapers, make sure to wash hands.

At night, wear close-fitting underwear. Be sure to change underwear every morning.

Cotton gloves may help prevent scratching during sleep.

Take a bath or shower regularly. Thoroughly clean the body, paying particular attention to the anal and vaginal areas. Showering is preferred to avoid contaminating bath water.

Do not share towels or face flannels.

Toothbrushes should be kept in a closed cupboard and rinsed well before use.

When the infestation has gone, good hand-washing practice and hygiene will help prevent re-infection. Good hygiene can prevent another outbreak even if children pick up another pinworm infection from friends at school.


The cause of pinworm infection is inadequate hygiene.

Eggs are transferred from the anus of an infected person to either their own mouth, re-infecting themselves, or another surface. If somebody else touches that contaminated surface and then touches their mouth, they may have ingested the eggs and can become infected.

The female pinworm lays eggs around the anus and vagina. The eggs can be transferred from the person’s anus to:

bed sheets




underwear and clothes

The female pinworm releases an itchy mucus when laying her eggs, triggering an urge to scratch the affected area of the anus or vagina. From the hands, the eggs may be transferred to anything that is touched, including:

bathroom utensils, such as toothbrushes, combs, and brushes

directly to other people’s hands


kitchen and bathroom surfaces

kitchen utensils


Swallowing the eggs

The eggs can survive for up to 3 weeks on surfaces. If they are touched, they will be transferred to the hands. If the hands then touch the person’s mouth, there is a serious risk of swallowing the eggs and becoming infected.

Breathing in the eggs

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