Pinworms

Topic Overview

What are pinworms?

Pinworms are a type of parasite that lives in the digestive system of humans. They are common throughout the world, especially in school-age children.

Adult pinworms look like small, white threads that are no more than 0.5 in (12.7 mm) long. You need a microscope to see the eggs.

What causes pinworms?

Most people get pinworms by swallowing the worms’ eggs. This happens when someone with pinworms scratches around the anus, gets eggs on his or her hands (or under the fingernails), and touches you or a surface that you later touch. When eggs get on your hands or food and then you eat, the eggs go into your mouth. And they move into your stomach and then to your rectal area.

The eggs turn into worms in about a month. A pinworm crawls out of the body during the night and lays eggs on the skin around the anus. The wiggling motion when the worm lays eggs may irritate the skin and cause itching.

Pinworms spread easily in families, day care centers, schools, camps, and other places where groups of people live. If one person in your family has pinworms, others probably do too. Pinworm infections can happen to anyone. They are not related to being unclean.

What are the symptoms?

The most common sign of pinworms is itching around the anus. Many people with pinworm infections have no symptoms and may never be aware of the infection. In rare cases, itching becomes severe and may cause restless sleep, loss of appetite, and anxiety.

Pinworms don't usually cause serious health problems, and they do not carry disease. But it is possible to get a skin infection from scratching around the anus.

The incubation period—the time from first contact with eggs until symptoms appear—is usually 1 to 2 months or longer. There is no way to find a pinworm infection until symptoms appear.

How are pinworms diagnosed?

Your doctor can find out if you have a pinworm infection by asking about your past health and checking the skin around your anus. He or she may ask you to collect a sample from around the anus by using a piece of clear, sticky tape. This piece of tape will be put under a microscope to look for pinworm eggs.

How are they treated?

You can treat pinworm infections with over-the-counter and prescription medicines. These medicines can help keep you from getting infected again and from spreading pinworms to other people.

How do you keep from spreading pinworms or getting them again?

To limit the chances of getting pinworms or of spreading them to others:

• Wash your hands carefully and often.
• Avoid scratching around your anus.
• Keep your fingernails short.
• Wash clothes and bedding regularly.
• Bathe and change your underwear every day.

If family members get pinworms again, all family members will need to take medicine to kill pinworms.

Frequently Asked Questions

Cause

Pinworm infections are usually caused by swallowing the eggs of the pinworm (Enterobius vermicularis) after coming in contact with an infected person or with an object that has eggs on its surface. Infection can also be spread when a person inhales airborne eggs, but this is rare. In rare cases, pinworm infection persists because eggs hatch outside the anus and the young worms crawl back inside the body.

Symptoms

Pinworms do not usually cause any symptoms beyond minor itching around the anus. Many people with pinworm infections have no symptoms and may never be aware of the infection. The infection can go away without treatment.

The most common symptoms of pinworm infection in children include:

• Itching around the anus. For most children this symptom is mild. Only in rare cases do children have very severe itching.
• Restless sleep (itching is often worse at night).

Other possible symptoms that may be present but are much less common include:

• Loss of appetite.
• Itching in the genital area.
• Pain or burning when urinating.
• Worms in stool (rarely seen).
• Skin rash (hives).
• Grinding of the teeth.
• Bed-wetting.
• Abdominal pain (rare, except when complications develop).

The above symptoms may result in anxiety.

Other conditions with similar symptoms include hemorrhoids and infections caused by other intestinal parasites (Ascaris, Trichuris, or tapeworms).

What Happens

The time it takes from when the eggs first enter your body to the time that an adult female pinworm lays new eggs is about one month. The eggs of pinworms get into the body through the mouth and develop into worms in the lower digestive system. They begin growing in the small intestine and move into the large intestine, where they become adult worms. The worms live by eating nutrients found in your digested food.

Female pinworms crawl out of the body and lay their eggs during the night on the skin around the anus. The female worm's wiggling motion when laying eggs is believed to irritate the skin and cause itching. The eggs have a damp, sticky covering, so when children scratch the skin around the anus, eggs stick to their fingers and get stuck under their fingernails. The eggs can then be transferred into their mouths or onto objects such as faucets and food. The eggs can also stick to clothing, bedding, and furniture. The eggs can live up to 2 weeks outside the body if the environment is warm and damp.

How pinworms are spread

Pinworms are spread when someone with pinworms scratches around the anus, gets eggs on his or her hands (or under the fingernails), and touches another person or an object. Infection can occur when:

• An uninfected person puts a hand in the mouth after being touched by an infected person.
• An uninfected person touches a pet or an object (such as bedding, clothes, dishes, or toys) that carries pinworm eggs and then puts a hand in his or her mouth.
• Bedding or clothes of a person who has pinworms are fanned in the air. Eggs can float through the air and be swallowed by other people.

A person with pinworms can be reinfected by any of the means listed above or when eggs hatch on the skin around the anus and the young worms (larvae) crawl back into the body.

Pinworm infection is contagious as long as living pinworm eggs are spread to and swallowed by someone. Because the medicine to treat pinworm infection kills adult worms but not pinworm eggs, a person who has received one treatment for pinworms can still spread the infection. This is why it is important to wash your hands often when you know that someone is infected. A second treatment with medicine is needed about 2 weeks after the initial treatment to kill any worms that have hatched during that time.

Complications

Complications from pinworms are rare. The most frequent complications are bacterial infection around the anus or of the skin in the genital area. This is usually because of skin irritation or scratches from itching in these areas.

What Increases Your Risk

Factors that increase the risk of being infected by pinworms include:

• Age. Pinworm infections are most common in preschool and school-age children.¹
• Household contact. If one child in a home gets a pinworm infection, it is likely that other children in the home will have the infection. Parents are also more likely to get the infection.
• Attending day care centers, schools, and summer camps. Pinworms are easily transmitted and spread among groups of children.
• Living in an institution. Up to 50% of people living in an institution are infected by pinworms.¹

Factors that increase the risk of spreading pinworm infections include:

• Living in an institution. Pinworms are easily transmitted and spread where people are living in close conditions (such as institutions).
• Poor hygiene practices, especially poor hand-washing. An infected person can spread pinworms to others if he or she does not wash his or her hands well.
• Sharing bedding. Also, fanning the bedding of an infected person can release pinworm eggs into the air.

When To Call a Doctor

Call your doctor if:

• You or your child has symptoms of pinworm infection, you have not seen any worms, and you want to be evaluated. If this is a first infection, it is recommended that a doctor confirm the diagnosis.
• You see pinworms on your child (when bathing the anal area or wiping his or her bottom) or on your child's bedding or clothes.
• You have started over-the-counter medicine to treat the pinworms, and the infection has not cleared up. (Do not use an over-the-counter medicine for pinworms in a child younger than 2 without first talking to a doctor.)
• You have had a pinworm infection recently and now have symptoms of reinfection. It is recommended that a doctor confirm the diagnosis.
• Your doctor prescribed medicine for pinworms, and the infection has not cleared up within the expected time frame (usually within 4 to 6 weeks).
• You or your child is having side effects from medicine for pinworm infection.
• You or your child with a pinworm infection develops other symptoms.
  • Fever or abdominal pain may be a sign of complications of pinworm infection.
  • Redness, tenderness, or swelling in the genital area may be a sign of skin infection.
  • Itching in the genital area or vagina may be a sign of vaginal pinworm infection.
  • Pain when urinating, frequent or urgent urination, or lack of control of urination may be signs of pinworm infection of the urinary tract.

Watchful Waiting

Watchful waiting is not appropriate when a person has symptoms of a pinworm infection. Although pinworm infections are usually mild and do not cause any serious health problems, treatment should be considered because it helps stop the spread of the infection to others and helps prevent reinfection.

Watchful waiting may not be appropriate for family members of a person infected with pinworms. If one member of a family has a pinworm infection, it is very likely that other members also are infected. This is very important if a family member is pregnant. A pregnant woman may not be able to take pinworm medicine, and treating all other members of the household may decrease the likelihood of her getting the infection. Most doctors recommend treating all members of the family to help prevent reinfection and the spread of infection.

Who To See

Health professionals who can diagnose and treat pinworm infections include:

• Nurse practitioners (NP).
• Physician assistants (PA).
• Pediatricians.
• Family medicine doctors.
• Internists.

If complications of pinworm infection develop, you may need to see a specialist who deals with conditions affecting the body system involved, such as:

• A gastroenterologist.
• A urologist.
• An infectious disease specialist.
• A gynecologist.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

When pinworm infection is suspected, the doctor will find out your or your child's medical history and do a physical examination. During the physical exam, your doctor will examine the skin around the anus for redness and irritation. Also your doctor may ask you to collect a sample by using a piece of transparent adhesive tape. This test, sometimes called a cellophane or “Scotch tape” test, involves pressing a piece of transparent adhesive tape on the skin around the anus in the morning before you or your child gets up or bathes. This piece of tape is then viewed under a microscope to look for pinworms and their eggs. Using this test for 3 days in a row will successfully diagnose pinworms 90% of the time.²

Other tests may be done if the physical exam and cellophane test have not shown pinworms and an infection is still suspected.

• Stool sample. Although collecting a stool sample may be useful, it is usually not the best way to diagnose pinworms since female pinworms do not lay many eggs in the rectum.
• Examination of the lower intestine (colonoscopy). This test is done in only very rare cases of pinworms that have not cleared up with treatment or in cases where the diagnosis is unclear.

If a complication of pinworm infection is suspected, more tests may be done. The specific tests that are needed will depend on the person's symptoms and the part of the body that is affected.

Treatment Overview

Pinworms can be successfully treated with:

• Medicine. Both over-the-counter and prescription medicines are available in liquid, chewable tablet, and pill forms. Women who are pregnant or breast-feeding and children younger than 2 should not take over-the-counter medicine without first talking to a doctor about the risks and benefits of the medicine.
• Steps to prevent reinfection and the spread of infection, including frequent hand-washing and routine washing of clothes and bedding. These measures are important and helpful even if medicine is not being used.

Pinworms are treated with medicine when:

• Signs and symptoms of pinworm infection are present, such as itching around the anus.
• Pinworm infection of family members and other close contacts is likely.

If severe itching is present, your doctor may prescribe a soothing cream to be applied to the anal area. If complications of pinworm infection develop, additional treatments may be needed.

Children can return to school after taking the first dose of medicine, bathing, and trimming and scrubbing their nails. At that time they can also take part in regular activities, such as swimming, sports, and after-school events.

What To Think About

Many people with pinworm infections do not have symptoms and do not need treatment to cure the infection. The infection may go away on its own, although this may take up to 14 weeks (two pinworm life cycles).

Many doctors suggest treating all close contacts of a person with pinworms even if there are no symptoms. Treating contacts with over-the-counter medicine can help prevent reinfection and the spread of pinworms to other people. This is especially important in households where pinworm infections come and go.

Treatment of all household members is also important if someone in the household is pregnant, breast-feeding, or younger than 2. These people may not be able to take pinworm medicine, and their chance of infection may be lower if all other members of the household are treated.

It is usually suggested that people with symptoms get a second treatment 2 weeks after the first treatment to kill any adult worms that may have hatched from eggs during that time. Pinworm medicine does not kill pinworm eggs.

Prevention

Most pinworm infections cannot be prevented. In families with more than one child, it is likely that a family member will get a pinworm infection at least once. Pinworm infections may not cause noticeable symptoms and often go away on their own. For more information, see the Home Treatment section of this topic.

Home Treatment

For people with pinworm infections, home treatment is very important to prevent reinfection and the spread of infection to other members of the household. Good home treatment includes the following measures:

• Wash hands carefully and often. Frequent hand-washing by all family members, especially before eating or preparing food and after using the toilet, is very important in preventing the spread of infection. Hand-washing will help remove eggs that may have stuck to the hands. Scrubbing your hands and fingernails for 1 minute is recommended.
• Control scratching. Itching around the anus caused by a pinworm infection usually occurs at night. Wearing gloves may help prevent scratching.
• Keep fingernails short. Pinworm eggs can get under the fingernails when the person with a pinworm infection scratches. Cutting the nails short may help prevent eggs from sticking under the nails. Discourage thumb-sucking if your child has a pinworm infection.
• Wash clothes and bedding. Washing underwear, pajamas, and bedding and drying them in a heated dryer on the first day of treatment may help prevent reinfection. Changing and washing underwear and pajamas at least once a day may also help prevent reinfection.
• Bathe carefully and every day. Make sure the skin around the anus is cleaned when bathing. This will remove pinworm eggs. Bathing in the morning may help get rid of a lot of the eggs. Showers may work better than baths because there is less chance of getting water that contains pinworm eggs into your mouth.
• Do not fan the bedding of an infected person. Fanning the sheets and blankets of an infected person can put pinworm eggs into the air. Airborne eggs can be swallowed when you breathe through your mouth.

Some doctors recommend extra housecleaning, such as frequent mopping and vacuuming and cleaning the toilet seat after each use, to prevent the spread of pinworms, but other doctors do not believe that these measures are very effective.

Preventing the spread of infection is especially important in households that include children younger than 2 or pregnant women, because they may not be able to take medicine for pinworms.

Medications

Medicine is often used for pinworm infections that are causing symptoms such as itching. Both over-the-counter and prescription medicines are available (in liquid, chewable tablet, and tablet forms). Most pinworm infections are cured with medicine.

Because medicines do not kill pinworm eggs, two doses are given, usually 2 weeks apart. The second dose is necessary to kill any worms that may have hatched from eggs after the initial treatment. In some cases of reinfection, 4 to 6 treatments (spaced 2 weeks apart) are necessary.

Medication Choices

Prescription medicines

Mebendazole

Albendazole (Albenza)

Nonprescription medicine

Pyrantel pamoate (Pin-X)

Do not use other medicines to treat pinworms without first speaking to your doctor. Piperazine and pyrvinium are no longer used to treat pinworm infections, but they may still be available in some pharmacies.

What To Think About

Mebendazole and pyrantel pamoate are the medicines most often used to treat pinworm infection. Both are very effective and have few side effects.

Pinworm medicine is not recommended for use by pregnant women, breast-feeding women, or by children younger than 2 without talking to a doctor about the risks and benefits of medicine. These groups are advised to use measures to prevent reinfection rather than using medicine. For more information, see the Home Treatment section of this topic.

Surgery

Surgical treatment to treat complications due to pinworm infection is uncommon. The surgery needed would depend on the type of complication.

Other Treatment

If severe itching is present, your doctor may prescribe a soothing cream to be applied to the anal area. If complications of pinworm infection develop, other treatments may be needed.

Other Places To Get Help

Organizations

Related Information

• Rectal Problems

References

Citations

1. American Academy of Pediatrics (2006). Pinworm infection (Enterobius vermicularis). In LK Pickering, ed., Red Book: 2006 Report of the Committee on Infectious Disease, 27th ed., pp. 520–522. Elk Grove Village, IL: American Academy of Pediatrics.
2. Dent AE, Kazura JW (2007). Enterobiasis (Enterobius vermicularis). In RM Kliegman et al., eds., Nelson Textbook of Pediatrics, 18th ed., pp. 1500–1501. Philadelphia: Saunders Elsevier.

Other Works Consulted

• Abramowicz M (2007). Drugs for parasitic infections. Treatment Guidelines From the Medical Letter, 5(Suppl): e1–e15.
• Katz M, Hotez PJ (2004). Parasitic nematode infections. In RD Feigin et al., eds., Textbook of Pediatric Infectious Diseases, 5th ed., vol. 2, pp. 2782–2797. Philadelphia: Saunders.
• Van Voorhis WC, Weller PF (2005). Helminthic infections. In DC Dale, DD Federman, eds., ACP Medicine, section 7, chap. 35. New York: WebMD.

Credits