Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 29, 2016

Pinworm infection is also known as enterobiasis. Knowing more about the infection will help an infected person understand the symptoms, how it is diagnosed and treated, and more.


Definition & Facts

Pinworm infection is a worm infection that occurs in the intestine and anal area. It is the most common worm infection in the United States and one of the most common in the rest of the world as well. Pinworms are small, typically between 1/4 and 1/2 inch in length, and they can be seen with the naked eye. They are white, thin, and look like a worm. Although pinworms can be seen, their eggs are extremely small and can only be seen using a microscope.

When a person with pinworm infection is sleeping, the female pinworms will be in the folds of the skin that surrounds the anus laying their eggs. The pinworms feed off of the infected person by absorbing the nutrients the person's body contains.

Symptoms & Complaints

A person that is infected with pinworms may not show any type of symptoms. But for those that do have symptoms, they are often:

A pinworm infection typically does not cause serious problems. In cases where the infestation is heavy in women, the infection can move from the intestines and anus to the organs of the female reproductive system. The pinworm will come out from the anus, move into the vagina and then up to the uterus, Fallopian tubes, and near the pelvic organs. This infection can then cause the vagina and inside lining of the uterus to become inflamed.


Pinworm infection is highly contagious and is transferred from one person to another through the eggs that the female pinworm lays via the fecal-oral route. Because the eggs are microscopic in size, they can be easily transferred without even knowing it.

Pinworm eggs can accidentally be breathed in or swallowed, causing the transfer of the infection. The eggs can also be ingested by being on food, drinks, or even fingers that are then put into a person's mouth. After the eggs have been swallowed, they will make their way into the intestines where they will hatch and then mature into worms. This process will happen over a period of a few weeks.

When the female pinworm lays its eggs in the skin folds of the anus, it often causes itching. When the infected person itches their anal area, they will then get the eggs under their fingernails and the eggs can cling to their fingers. The eggs can then be transferred to other surfaces, such as toys, toilet seats, and faucet handles, as well as to food, clothing, and people. The eggs of a pinworm can live between two and three weeks on a surface.

Young children are at greatest risk of getting pinworm infection. Because of the highly contagious nature of this infection, everyone that lives in the same household or is at the same school or daycare center as an infected child is at great risk too.

Diagnosis & Tests

When the potentially infected person goes to the doctor to determine the cause of their symptoms, they should be prepared to answer a variety of questions that may be asked, including:

  • When did the patient first notice the itching?
  • Is the itching normally happening at night?
  • Has there been anything that has made the itching or other symptoms better or worse?
  • Does anyone else in the family have symptoms that are the same?
  • Has the patient or anyone else in the family been in contact that is known to have pinworms?
  • Have any dead worms been found in the toilet, underwear, or clothes worn at bedtime?

In order for a doctor to test and verify whether or not a person has a pinworm infection, they need to be able to see the worm or the eggs. The easiest way for this to happen is by using a piece of transparent tape to gather a sample. The tape test should be done right away in the morning before the possibly infected person goes to the bathroom or cleans up in any way. Tape should be put on the skin around the anus.

It is best to do this test for three days in order to get a good sample. The tape should be brought with to the doctor appointment. The doctor will then be able to look at the tape under the microscope to see if there are any eggs.

Treatment & Therapy

Once pinworm infection has been diagnosed, the doctor will either prescribe a medication or advise that the infected person pick up an over-the-counter drug, pyrantel pamoate that will kill the eggs and pinworms. The two types of antiparasitic prescription drugs that are most often used are mebendazole and albendazole. In order to ensure that all of the pinworms and eggs have been killed, two doses are usually prescribed.

Because of the highly contagious nature of a pinworm infection and that the eggs can not be seen with the naked eye, it is important that other precautions are taken as well. When one person is diagnosed with pinworm infection, a doctor will often give a prescription for everyone living in the home. It is also important for clothing that has been worn, as well as all of the bedding, to be washed before it is used again. The surfaces of the home should be washed down as well as toys of any infected child.

Prevention & Prophylaxis

Pinworm eggs will stick to all surfaces, such as toys, bedding, faucets, and toilet seats for two weeks, so it is important to wash surfaces as often as possible. In order to further prevent contamination, there are some other things that can be done as well.

  • Take showers in the morning. Pinworms lay their eggs at night, so it is best to shower and wash your anal area in the morning.
  • Change bedding and underwear everyday. This will help to remove any eggs.
  • Wash everything with hot water and dry on high heat. This will help kill the eggs.
  • Try not to itch the area around the anus. Keep kids' fingernails cut short to help reduce the area any eggs can collect.
  • Always wash hands after changing a diaper, using the bathroom, and before eating. This will help to kill any eggs that may have been picked up.