Pinworm Infection

What Are Pinworms?

Picture of Pinworms Life Cycle
Picture of Pinworms Life Cycle
  • Pinworm (Enterobius vermicularis) infections are the most common worm infection in America.
  • Although any individual may develop a case of pinworms, the infection occurs most frequently in school children between 5 to 10 years of age.
  • Pinworm infections occur in all socioeconomic groups; however, human-to-human spread is favored by close, crowded living conditions. Spread among family members is common.
  • Animals do not harbor pinworms - humans are the only natural host for this parasite.
  • The most common symptom of pinworms is an itchy rectal area. Symptoms are worse at night when the female worms are most active and crawl out of the anus to deposit their eggs.
  • Although pinworm infections can be annoying, they rarely cause serious health problems and are usually not dangerous.
  • Therapy with routine prescription medications provides an effective cure in almost all cases.

What Causes Pinworms?

Pinworms Causes
Since pinworm infection is highly contagious, it is not unusual for adults, who are potentially exposed to those with an infection, to become infected themsleves.

The very simple life cycle of E. vermicularis ensures a high human prevalence. Tiny eggs deposited around the anus by a female worm spread the infection. Each female worm can produce more than 10,000 eggs during her lifespan. When someone with pinworms scratches their perianal area, eggs may lodge under their fingernails and be spread to anything he or she touches. Infested dust, clothing, bedding, or toys can also spread eggs. When someone else accidentally ingests these eggs, they also become infected.

Over the next several weeks, newly ingested eggs hatch and mature into adult worms. The new worms migrate to the junction between the small and large intestine. Following further maturation, the newly "pregnant" worm migrates from this region to the rectum. From here she will make the trip to the anal area (commonly at night) and deposit her eggs. The life cycle has now come full circle. Adult females live for approximately three months in their human host. Their eggs may die within one to two days in a warm and dry environment; however cool and humid conditions will allow their survival for up to two weeks.

Can Adults Get Pinworms?

Since pinworm infection is highly contagious, it is not unusual for adults who are potentially exposed to those with an infection (for example, parents and caregivers) to themselves become infected. Since most pinworm infections are asymptomatic, statistics regarding infection under such circumstances are not exact.

What Are Symptoms of Pinworm Infections?

Symptoms of Pinworms
The most common symptom of pinworms is itching around the anus.

Many people have pinworms and don't have any symptoms at all.

  • The most common symptom of pinworms is itching around the anus. It is worse at night when the female worm deposits her eggs on the person infected. This can lead to difficulty getting a good night's sleep. This intense itching is felt to be due to an inflammatory response to the adult worm and her eggs in the perianal tissue. If severe scratching occurs, the skin may break down and allow development of a secondary bacterial infection.
  • Pinworms can rarely migrate into the vagina or urinary tract causing irritation in these regions. Intense itching is again the prominent complaint. This location of infection is less common than the perianal region, and the infection usually goes away on its own. Case reports of E. vermicularis migration into the internal female reproductive tract have been reported. These infections are very rare.
  • Pinworms do not cause abdominal pain, bloody bowel movements,fevers, or poor appetite. If the person has any of these signs or symptoms, they may have a more serious condition and should call a doctor or visit the hospital's emergency department. Adult pinworms have been found in inflamed appendices removed at operation; however, whether the pinworm infection was the cause of appendicitis is controversial.

When to Seek Medical Care If You Think You Have Pinworms

  • If you suspect that you or your child might have pinworms, you should make an appointment to see your doctor.
  • To help the doctor make the diagnosis, look for these signs:
  • Pinworms are big enough to be seen with the naked eye. They are yellow-white and look like a fine piece of thread. They are usually less than one-half inch long.
  • Pinworms are most active at night. The best time to see them on the anus is a few hours after bedtime. Parents sometimes try to sneak up on the worms by throwing back the child's bedcovers and shining a flashlight on a bare bottom in hopes of catching the culprits in action.
  • Pinworms can also sometimes be seen on the outside of a child's stool.

Which Specialties of Doctors Treat Pinworms?

Pediatricians, family practioners and internists are all capable of accurately diagnosing and treating pinworm infections. Since simple antibiotics are very successful at curing the infection and complications are unusual, specialists are rarely necessary.

How Are Pinworms Diagnosed?

  • If a person suspects pinworms but does not see them, the "tape test" can be used.
    • It is best done at night during the characteristic intense itching or early in the morning before any bathing or washing.
    • Wrap a piece of cellophane tape around a tongue depressor, sticky side out, and press it to the skin around the anus to collect any eggs.
    • Take the tape to a doctor, who will put it under a microscope to look for pinworm eggs.
    • The doctor may ask the person to use several pieces of tape to increase the likelihood of seeing the eggs. A single specimen will detect approximately 50% of cases; 90% of cases will be detected if the test is repeated three times.
    • Blood tests are not necessary to establish the diagnosis of pinworm infection.
  • The doctor may decide based upon the patient's symptoms that pinworms are present and may treat with medication without doing any tests.
  • If one person in a household has pinworms and other people in the household have the same symptoms, it is not necessary to test everyone before treating.

How to Treat Pinworm Infection in Children and Adults?

  • albendazole (Albenza) is the most common treatment for pinworms.
    • Treatment is a single tablet, which kills the worms. There are different strengths for adults and children younger than two years of age.
    • Because eggs can survive for a few weeks, the patient will have to take a second dose two weeks later to lessen the chance of reinfection.
  • mebendazole (Vermox) also works. It is also taken in a single dose and repeated two weeks later.
  • Because it is common for everyone in a household to have pinworms at the same time, the doctor may recommend that everyone be treated at the same time.
  • The doctor may also recommend tap water enemas to help flush out the pinworms and reduce symptoms.
  • After taking the pills, the patient should also do the following:
    • Get into the habit of carefully washing the hands after using the toilet, and before and after eating.
    • Thoroughly launder all bedding, clothing, and toys to destroy any lingering eggs.
    • Launder all bedding every 3-7 days for three weeks.
    • Wash underwear and pajamas daily for two weeks.

Previously used drugs [pyrantel pamoate (Pin-Rid, Pin-X) and piperazine] are now rarely used due to lower efficacy and a higher frequency of side effects when compared to albendazole (Albenza) or mebendazole (Vermox).

Can a Child or Adult Become Reinfected with Pinworms?

  • It is common to become reinfected with pinworms several months after treatment.
  • If the symptoms recur, should call a doctor and be treated again.

What Can You Do to Prevent Getting Pinworms?

  • Practice good hygiene. Washing your hands before eating or preparing meals helps prevent spread of infection.
  • Avoid scratching the anal region.
  • Avoid biting the fingernails.
  • Keep fingernails short and clean.
  • Wash all bedding and pajamas regularly.
  • Be sure your child changes underwear daily.
  • Frequently vacuum the play area.
  • Despite these measures, it still may be quite difficult to avoid reinfecting yourself or spreading pinworms to others.

What Is the Outlook for a Person Who Gets Pinworms?

  • Pinworm infections are easy to treat, and the pinworms go away.
  • Because the pinworm infection is so highly contagious, it is not unusual for infections to recur.

Anal Itching Causes

When a cause can be found, the itching is usually due to irritation of the skin around the anus.

A variety of problems can cause anal itching, for example, pinworms, perfumes, diarrhea, hemorrhoids, cancer, and some foods like caffeine and chocolate.

Huh, Sun. "Pinworm (Enterobiasis)." Medscape. Aug. 16, 2017. <>.