Encyclopedia / P / Pinworms



Pinworms are slender, white, threadlike worms about a third of an inch long that can infest the intestinal tract. Pinworm, the most common worm infection in the U.S., is a mild but annoying and disruptive childhood infection.


The human pinworm, Enterobius vermicularis, is a parasite that lives only in the human intestine, not outside the body. Pinworm in animals does not affect humans.

People blame pinworms for such childhood problems as teeth grinding, bed wetting, stomach aches, weight loss, poor appetite, and even appendicitis, but there is no proof that pinworm is responsible for these conditions.

Infestation with these parasites begins when pinworm eggs are swallowed and lodge in the intestine, where they hatch and mature. Two to six weeks later, the adult female worm exits down the digestive tract to the skin folds of the anal region, where she deposits her eggs in a sticky substance and then dies.

The eggs sit in the anal area for as long as three weeks before hatching. After hatching, the worms move back to the lower intestine.

School-age children are most often infected. Next are preschoolers, especially those in daycare centers. The infection is so common that in some schools more than half the children may be infected.

Pinworms are more a nuisance than a serious health problem. The main complaint is that of intense anal itching, due to the irritation caused by worms migrating across the skin.

In general, the body's immune system eliminates pinworms living within the intestine within several months. However, eggs are usually dispersed in bedding material or clothing and may spread via the fingers or even through the air, making reingestion of eggs and a new cycle of infection common - not just among those who were originally affected but among other members of the household as well.


Swallowing pinworm eggs initiates a cycle of infection. Most often, eggs are spread when a child scratches the anus, allowing the eggs to be transported on the fingers or beneath the fingernails, where they can then contaminate food, dishes, toys, and play areas.


Symptoms include anal or vaginal itching and irritation, as well as possible irritability, fatigue, weight loss, behavior problems and night-waking/nightmares.


A laboratory pinworm test called a "scotch tape test" can be done. The doctor or a parent can perform this test.

Parents can obtain the needed scotch tape paddle from their doctor. The paddle is pressed against the anal area to collect eggs or live pinworms. Do this test in the morning (for two days in a row) before the child baths or has a bowel movement. Take the tests to the doctors for examination with a microscope.


Everyone in the family is treated with anti-worm drugs, since other family members are at high risk of being infected.

Usually, a dose of mebendazole (Vermox) or pyrantel pamoate (Antiminth, Combantrin) is given, followed by a second dose two weeks later. These medicines are very effective in killing worms. Piperazine and pyrvinium are less effective choices.

Creams or ointments that relieve anal itching and may contain substances that kill the worms can be prescribed. Careful hygiene is essential to prevent reinfection.

Trim the child's fingernails so that he or she will not be harmed by scratching. Soothe the itching and any rectal pain by giving the child a sitz bath and cleaning the anal opening with witch hazel.

Change the child's bed linen and underwear daily, and try not to disperse the eggs into the air.


Does the child have pinworms?

What is the probable source of the infestation?

Will you prescribe anti-worm drugs?

How do these work?

Can you prescribe a soothing cream?

What precautions should be taken to prevent reinfestation?

To check your child for pinworms, you will look for a 1/4" white threadlike worm that moves.

The best time to see these pinworms is in the middle of the night when they are most active. If the child wakes up with an itchy anal area, turn them over on the stomach. Tuck their knees under the chest a little, spread the buttocks so you can clearly see the anal area. Shine a bright flashlight on this area - if you see little white threadlike worms, the child has pinworms.