How long after exposure to pinworms do symptoms appear?


Frequently asked questions about pinworm infection

Who should not take EMVERM?

Do not take EMVERM if you are allergic to mebendazole or any of the ingredients in EMVERM. See the end of this Patient Information for a complete list of ingredients in EMVERM.

Before you take EMVERM, tell your healthcare provider about all of your medical conditions, including if you:

  • are pregnant or plan to become pregnant. It is not known if EMVERM will harm your unborn baby.
  • are breastfeeding or plan to breastfeed. EMVERM can pass into your milk and may harm your baby. Talk to your healthcare provider about the best way to feed your baby if you take EMVERM. Do not breastfeed while taking EMVERM.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
Using EMVERM with certain other medicines can change the way these medicines act, causing serious side effects.
Know the medicines you take. Keep a list of them to show to your healthcare provider or pharmacist when you get a new medicine.

How should I take EMVERM?

  • Take EMVERM exactly as your healthcare provider tells you to take it.
  • Take EMVERM by mouth with or without food.
  • EMVERM tablet may be chewed, swallowed, or crushed and mixed with food.
  • If you take too much EMVERM, you might have symptoms that include stomach cramps, nausea, vomiting or diarrhea.

What should I avoid while taking EMVERM?

Do not take EMVERM with metronidazole (a medicine used to treat bacterial and protozoan infections) as serious skin reactions called Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) can happen.

What are the possible side effects of EMVERM?

EMVERM may cause serious side effects, including:

  • Low white blood cell count (neutropenia). Neutropenia can cause you to get other infections. Your healthcare provider will check your blood count regularly during your treatment with EMVERM. Tell your healthcare provider right away if you have a fever or any signs of an infection while taking EMVERM.
  • Severe skin reactions (Stevens-Johnson syndrome and toxic epidermal necrolysis). EMVERM may cause rare, but serious skin reactions when taken with metronidazole and other medicines that contain mebendazole. These severe allergic reactions may be life-threatening and need to be treated in a hospital. Call your healthcare provider right away or get emergency medical help if you have any allergic reactions or the following symptoms:
    • severe skin blisters
    • sores around the mouth, nose, eyes, vagina or penis (genitals)
    • peeling skin
    • swollen face, lips, mouth, tongue or throat
    • itchy rash (hives)

The most common side effects of EMVERM include:

  • loss of appetite (anorexia)
  • stomach pain
  • diarrhea
  • passing gas
  • nausea
  • vomiting
  • rash

Tell your healthcare provider if you have any side effect that bothers you or does not go away.“
These are not all the possible side effects of EMVERM.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store EMVERM?

  • Store at room temperature between 68°F to 77°F (20°C to 25°C).
  • Safely throw away medicine that is out of date or no longer needed.

Keep EMVERM and all medicines out of the reach of children.

General information about the safe and effective use of EMVERM.

Medicines are sometimes prescribed for purposes other than those listed in the Patient Information. Do not use EMVERM for a condition for which it was not prescribed. Do not give EMVERM to other people, even if they have the same symptoms that you have. It may harm them. You can ask your pharmacist or healthcare provider for information about EMVERM that is written for health professionals.

What are the ingredients in EMVERM?

Active ingredient: mebendazole.
Inactive ingredients: microcrystalline cellulose, corn starch, anhydrous lactose NF, sodium starch glycolate, magnesium stearate, stearic acid, sodium lauryl sulfate, sodium saccharin, and FD&C Yellow #6.

What is EMVERM?

EMVERM is a prescription medicine used to treat adults and children 2 years of age and older with intestinal worm infections caused by pinworm, whipworm, roundworm, or hookworm.

To report SUSPECTED ADVERSE REACTIONS, contact Amneal Specialty, a division of Amneal Pharmaceuticals LLC at 1-877-835-5472 or FDA at 1-800-FDA-1088 or

How Pinworms Are Diagnosed

You have to see the eggs or worms to make the diagnosis. The best way to do this is by doing a tape test. In the morning, before your child goes to the bathroom or washes up, put the sticky side of a piece of clear tape around the anus. Remove the tape and look for pinworms or their eggs. You can also buy a tape test kit at the pharmacy. If you do not find pinworms, do the tape test 2 more mornings in a row, to be sure.

How to Treat the Infection

  • Your child’s doctor will prescribe a special medicine to treat pinworm infection.The dose is based on the person’s weight.Usually 2 doses of the medicine are ordered.The second dose starts 2 weeks after the first.
  • Read the label on the bottle of medicine to know how to give it.
  • Your child’s doctor will also treat other family members and close contacts with the same medicine, at the same time.

How to Prevent Reinfection or Spreading Pinworms to Others

It is easy to be reinfected with pinworms or spread them to others. During treatment and for 2 weeks after treatment is finished, do the following:

  • Hand washing is most important.Have your child and all family members wash their hands often.They should wash before meals or eating, after using the toilet and after scratching (Picture 1). This is a good habit to do at all times.
  • Keep your child’s fingernails clean and cut as short as possible.
  • Teach your child to avoid touching his mouth or biting his fingernails.
  • Have your child shower or bathe every morning.
  • Do not let children bathe together or share items.
  • Clean the anus with soap and water after each bowel movement.Use clean washcloths or paper towels each time.
  • Scrub the toilet seat daily with disinfectant or soap and water (Picture 2).
  • Wipe down any toys that your child usually puts in his mouth or hard surfaces that he has touched with disinfectant or soap and water.
  • Change bed linens and put clean underwear and clothes on every day.Avoid shaking these things so that eggs are not put into the air.
  • Promptly wash used bed linen, all clothing, towels and washcloths in hot water with detergent.
  • Vacuum carpets and floors well.Wash the canister or change the vacuum cleaner’s bag after each use.Seal the bag before throwing it away.
  • Wash any raw vegetables or fruits thoroughly before eating.
  • Call your child’s school or childcare center so that they can take extra steps to prevent the spread to others.Your child can return to school or childcare 24 hours after treatment.

When to Call Your Child’s Doctor

  • If you see pinworms
  • If anal itching lasts more than 1 week
  • If the skin around the anus becomes red or tender

Pinworms: Treatment and Prevention (PDF)

HH-I-56 10/78, Revised 3/19 Copyright 1978-2011, Nationwide Children’s Hospital



Contraindication: EMVERM is contraindicated in persons with a known hypersensitivity to the drug or its excipients (mebendazole, microcrystalline cellulose, corn starch, anhydrous lactose, sodium starch glycolate, magnesium stearate, stearic acid, sodium lauryl sulfate, sodium saccharin, and FD&C Yellow #6).

Warnings and Precautions:

  • Risk of convulsions: Convulsions in infants below the age of 1 year have been reported

  • Hematologic effects: Neutropenia and agranulocytosis have been reported in patients receiving mebendazole at higher doses and for prolonged duration. Monitor blood counts in these patients

  • Metronidazole and serious skin reactions: Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) have been reported with the concomitant use of mebendazole and metronidazole

Adverse Reactions from Clinical Trials*: Anorexia, abdominal pain, diarrhea, flatulence, nausea, vomiting, rash.
Adverse Reactions from Postmarketing Experience with Mebendazole*: Agranulocytosis, neutropenia, hypersensitivity including anaphylactic reactions, convulsions, dizziness, hepatitis, abnormal liver tests, glomerulonephritis, Stevens-Johnson syndrome/toxic epidermal necrolysis, exanthema, angioedema, urticaria, alopecia.
*Includes mebendazole formulations, dosages and treatment duration other than EMVERM 100 mg chewable tablet.

Drug Interactions: Concomitant use of EMVERM and metronidazole should be avoided.

Use in Specific Populations:

  • Pregnancy: Mebendazole use in pregnant women has not reported a clear association between mebendazole and a potential risk of major birth defects or miscarriages. However, there are risks to the mother and fetus associated with untreated helminthic infection during pregnancy.

  • Lactation: Limited data from case reports demonstrate that a small amount of mebendazole is present in human milk following oral administration. There are no reports of effects on the breastfed infant.

  • Pediatric Use: The safety and effectiveness of EMVERM 100 mg chewable tablet has not been established in pediatric patients less than two years of age.

  • Geriatric Use: Clinical studies of mebendazole did not include sufficient numbers of subjects aged 65 and older to determine whether they respond differently from younger subjects.

Overdosage: In patients treated at dosages substantially higher than recommended or for prolonged periods of time, the following adverse reactions have been reported: alopecia, reversible transaminase elevations, hepatitis, agranulocytosis, neutropenia, and glomerulonephritis.

  • Symptoms and signs of overdose: In the event of accidental overdose, gastrointestinal signs/symptoms may occur

  • Treatment of overdose: There is no specific antidote

Patient Counseling: Healthcare professionals should advise the patient to read the FDA-approved patient labeling (Patient Information). Advise patients that:

  • Taking EMVERM and metronidazole together may cause serious skin reactions and should be avoided.

  • EMVERM can be taken with or without food.


EMVERM is indicated for the treatment of patients two years of age and older with gastrointestinal infections caused by Ancylostoma duodenale (hookworm), Ascaris lumbricoides (roundworm), Enterobius vermicularis (pinworm), Necator americanus (hookworm), and Trichuris trichiura (whipworm).

To report SUSPECTED ADVERSE REACTIONS, contact Amneal Specialty, a division of Amneal Pharmaceuticals LLC at 1-877-835-5472 or FDA at 1-800-FDA-1088 or

Please click here for Full Prescribing Information.

What Are Pinworms?

Pinworms are highly contagious and cause itchiness around the anus and vagina.

The term “pinworm” refers to Enterobius vermicularis, a tiny, threadlike, white roundworm (formally known as a nematode) that infects the intestines of people.

Pinworm infections are typically called enterobiasis, but are also sometimes known as oxyuriasis or threadworm.

Enterobiasis is the most common type of worm infection in the United States, according to the Centers for Disease Control and Prevention (CDC).

Among high risk groups — children under age 18, institutionalized people, and those who take care of infected people — the prevalence of pinworm infection can reach 50 percent.

How Do You Get Pinworms?

Enterobiasis is contagious, and the infection can be passed between people.

You get pinworms by ingesting E. vermicularis eggs — which are moist, highly resistant to drying out, and can remain viable in the environment for a long time, according to the National Institute of Allergy and Infectious Diseases.

Adult female pinworms deposit thousands of eggs on the perianal skin (the area around the anus). You may directly expose yourself to these eggs by scratching the contaminated area and then putting your fingers in your mouth.

Once on your fingers, the microscopic eggs can also transfer and attach to many different surfaces — including toys, bedding, clothing, towels, toilet seats, sandboxes, food, drinking glasses, and utensils — where they can survive for 2 to 3 weeks if the surfaces aren’t cleaned, according to the CDC.

The eggs can also become scattered into the air and inhaled.

Enterobius vermicularis Life Cycle

Pinworms can only infect humans.

Inside the body, E. vermicularis eggs hatch in the small intestine and take 1 to 2 months to mature. Adult pinworms then travel to the large intestine (colon) to mate.

At night — typically when their human hosts are asleep — pregnant female pinworms leave the anus to deposit their eggs in the perianal area.

The larvae inside these eggs can become infective in as little as 4 to 6 hours, the CDC notes.

It’s possible for the larvae to hatch and travel back into the rectum, but it’s unknown how frequently this occurs.

Pinworms Symptoms

Many people don’t develop any symptoms from enterobiasis, while others develop mild symptoms.

Itchiness around the anus and vagina — caused by the movement of pregnant female pinworms — is the most common symptom from a pinworm infection. This itchiness can:

  • Be intense
  • Disrupt sleep
  • Cause irritability
  • Lead to a bacterial infection from scratching

In rare cases, the nematodes can spread to the vaginal area and cause urinary tract infections.

They can also travel to the appendix and cause appendicitis-like symptoms — such as vomiting, abdominal pain, and reduced appetite — without causing any actual inflammation of the appendix.

Pinworms Treatment

Pinworms are treated with one of several antiparasitic medications, which are taken in two doses spread 2 weeks apart (the second dose kills eggs that may have hatched since the first dose).

These medications include:

  • Mebendazole
  • Albendazole
  • Pyrantel pamoate

Pyrantel pamoate is available without a prescription, but it’s not as effective as the other two medications, according to the CDC.

It’s important for all people within a household to be treated for pinworms, even if it’s not apparent that they’re infected and they don’t have any symptoms.

Good hygiene and proper care can help prevent the spread of pinworms and reinfection. Helpful steps include:

  • Cleaning toilets frequently
  • Showering every morning (showering is safer than taking a bath)
  • Carefully handling underclothing, night clothes, towels, and bedding (don’t shake them, or E. vermicularis eggs may become airborne), and washing them frequently
  • Avoiding scratching the perianal area
  • Keeping your fingernails short, and not biting them
  • Washing your hands appropriately, such as before and after eating and after going to the bathroom


Topic Overview

Pinworms are a type of parasite that lives in the digestive system of humans. They are common throughout the world.

Adult pinworms are about 0.5 in. (12.7 mm) long and look like little white threads. Pinworm eggs are so tiny, you’d need a microscope to see them.

What causes pinworm infection?

Most people get infected by accidentally swallowing pinworm eggs. Anyone can get pinworms, but they are most common in school-aged children. They are usually spread like this:

  • A child swallows pinworm eggs, and they travel to the child’s intestines. In about a month, the eggs hatch into worms. At night the female worms crawl out the rectum and lay eggs around the child’s anus.
  • When the worms lay eggs, it can cause itching. If the child scratches, the eggs can cling to the child’s fingers and get stuck under the fingernails.
  • The eggs then stick to things the child touches, such as clothing, dishes, toys, and furniture. The eggs can live 2 to 3 weeks outside the body.
  • When you touch something the child has touched, the eggs get on your hands. Then if you touch food or your mouth, you can swallow the eggs. This starts the cycle over again.

Pinworms spread easily in homes, day care centers, schools, and other places where groups of people spend time together. So if one person in your family has pinworms, others probably do too.

It’s possible to get pinworms by inhaling airborne eggs, but this is rare. It’s also rare to get pinworms from a swimming pool.

Pinworms are spread from person to person. Pets don’t get pinworms and can’t spread them to humans.

What are the symptoms?

Many people with pinworms don’t have symptoms and don’t know that they’re infected. When symptoms occur, the most common ones are:

  • Itching around the anus.
  • Restless sleep, because itching is often worse at night.

Pinworms can be annoying. But they don’t carry disease, and they rarely cause serious health problems. Sometimes people get a skin infection from scratching.

To find out if you have pinworms, your doctor will ask about your past health and check the skin around your anus.

The doctor may ask you to do a transparent tape test at home. To do the test, you press a piece of clear, sticky tape on the skin around your anus in the morning before you get up. The doctor will put the tape under a microscope to look for pinworm eggs. You might need to repeat this test a few times.

How are they treated?

You can treat pinworms with over-the-counter or prescription medicine that kills the worms. Treatment can help keep you from getting infected again and from spreading the infection to other people.

You will probably need two doses, 2 weeks apart. That’s because the medicine kills the worms but not the eggs. The second dose will kill any worms that hatch after the first treatment.

Pinworm medicine may not be safe for children younger than 2 and women who are pregnant or breastfeeding. So to reduce their risk of infection, a doctor may recommend that all other household members be treated with medicine.

Call your doctor if:

  • Medicine hasn’t cleared up the infection.
  • The medicine is causing side effects.
  • You have new or worse symptoms.

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

Pinworms spread easily and often come back. To reduce your chances of spreading the infection or getting infected again:

  • Wash your hands carefully and often. Teach your children to do the same, especially after they use the toilet and before they handle food.
  • Keep your fingernails short, and don’t scratch the itch. Wearing gloves at night may help prevent scratching.
  • Bathe or shower every day.
  • Don’t share or reuse towels or washcloths.
  • Change your underwear and bedding each morning.
  • Wash clothes, bedding, and towels regularly. Dry them in a hot dryer.

If anyone in your household gets pinworms again, the whole family may need to take medicine.

Enterobius vermicularis, also known as threadworms or pinworms, are the most common helminth infestation in the UK and usually present in children. As many as 40 per cent of young children in the UK could have suffered an infestation at some time.


  • The main symptom is intense perianal irritation, especially at night.
  • Good hygiene limits transmission, and is the only option for babies under three months and pregnant women, especially in the first trimester.
  • All members of a household must be treated.
  • Effective OTC preparations are available.
  • Piperazine and mebendazole are the treatments of choice.

1. The threadworm life cycle
The small (females about 10mm, males 4mm), white, thread-like worms can live for up to six weeks. One female can lay up to a thousand eggs, which are too small to be seen with the naked eye. The eggs can stick to fingers and fingernails from scratching, and transfer to the mouth, clothing and other surfaces. They can be easily transferred to other people if hygiene is poor.

Once one member of a household is affected the infestation will probably spread to the other occupants. Eggs may be transferred to objects, such as children’s toys, worktop surfaces and kitchen equipment, and they can remain viable for as long as three weeks.

Once hatched, worms reach maturity and produce more eggs in about a fortnight. If swallowed, the eggs hatch in the intestine; if eggs around the anus hatch, they can re-enter the gut.

2. Symptoms
The most common symptom is intense irritation around the anus (and vagina in females) at night, caused by female threadworms laying eggs around the anus. It is thought the associated mucus is the irritant that causes scratching, and the irritation may be severe enough to disturb sleep. In severe infestations there may be loss of appetite and weight, and irritability from lack of sleep.

3. Making the diagnosis
The typical symptoms in a child raise the possibility of threadworm infestation, and parents may suggest the diagnosis if their family has been affected before, or if a playmate of their child has recently been diagnosed.

Sometimes a parent has already looked for worms around the anus, sheets and bed clothes, or in the stool, and may even bring an example. However, threadworms are not easy to see. Female worms are normally seen, as the smaller male worms have no need to venture forth for egg-laying.

Laboratory confirmation of an obvious infestation is not always necessary, but is useful if the diagnosis is putative or disputed. A moistened swab from the anal region or a stool sample may reveal worms or eggs. The sticky tape test may be useful: the sticky side of some clear adhesive tape is applied to the area around the anus, preferably at night, with the hope that eggs will stick to it. When the tape is sent to the laboratory, eggs will be visible under microscopy.

4. Hygiene measures
Adhering to a strict hygiene protocol alone for about six weeks can eradicate an infestation in a family without medication, but generally there is pressure to prescribe.

The hygiene measures required involve washing all sleepwear, bed linen, towels and soft toys, thorough and repeated vacuuming, repeated damp-dusting of all surfaces, keeping nails short and discouraging thumb sucking and nail biting.

Cotton gloves worn at night may prevent scratching and hand contamination. Thorough hand-washing before eating and after using the lavatory and daily washing of anal and vaginal areas are essential. Towels, flannels and toothbrushes must not be shared. Ideally, such measures should be pursued in all households whether there is infestation or not, but standards tend to slip, even after an outbreak.

Pets do not catch or pass on threadworms, but eggs can attach to fur and be ingested from fingers after an animal is stroked.

5. Medical management
OTC preparations are available for self-treatment, and this is an approach often used by parents whose children have been previously affected, without consulting their GP. Pregnant or breastfeeding women and babies under three months should not take medication – hygiene measures are the only option for these groups.

Anthelmintics, such as piperazine or mebendazole, only kill the worms, not the eggs, so good hygiene is still an essential part of management. The whole household must be treated, whether they have symptoms or not.

Piperazine paralyses the threadworms, and is combined with senna to speed up gut transmission. It is suitable for children from the age of three months, and is given as a single dose, repeated after two weeks. Patients with epilepsy or hepatic or renal impairment should not take piperazine.

Mebendazole acts by preventing the absorption of glucose, which threadworms need to survive, and is preferred for children over the age of two years. A second dose is recommended after two weeks.

Dosage of both medications depends on age and is clearly stated on accompanying literature. Side-effects are rarely troublesome with either medication, but abdominal pain or diarrhoea may occur.

Involvement outside the bowel is rare, but may occur in the vagina, uterus and abdominal cavity, and even pulmonary and hepatic involvement has been reported. One question that is frequently asked by parents is whether they can still send their children to school and the answer, with which the Health Protection Agency agrees, is yes.

  • Dr Barnard is a former GP from Fareham, Hampshire

Pinworm Infections

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What Is a Pinworm Infection?

Pinworm is an intestinal infection caused by tiny parasitic worms. It’s a common infection that affects millions of people each year, particularly school-age kids.

If your child develops a pinworm infection, try not to worry. Pinworms don’t cause any harm (just itching and restless sleep), and it won’t take long to get rid of them.

How Do Pinworm Infections Spread?

Pinworm infections (also known as “seatworm infection” or “threadworm infection”) are contagious.

Pinworms get into the body when people ingest or breathe in the microscopic pinworm eggs. These eggs can be found on contaminated hands and surfaces, such as:

  • bed linens
  • towels
  • clothing (especially underwear and pajamas)
  • toilets
  • bathroom fixtures
  • food
  • drinking glasses
  • eating utensils
  • toys
  • kitchen counters
  • desks or lunch tables at school
  • sandboxes

The eggs pass into the digestive system and hatch in the small intestine. From the small intestine, pinworm larvae go to the large intestine, where they live as parasites (with their heads attached to the inside wall of the bowel).

About 1 to 2 months later, adult female pinworms leave the large intestine through the anus (the opening where bowel movements come out). They lay eggs on the skin right around the anus, which triggers itching in that area. Often, this happens at night.

When someone scratches the itchy area, microscopic pinworm eggs transfer to their fingers. Contaminated fingers can then carry pinworm eggs to the mouth, where they go back into the body, or stay on various surfaces, where they can live for 2 to 3 weeks.

If you’re wondering if your family pet could give your child a pinworm infection, it can’t. Pinworms don’t come from animals.

What Are the Signs & Symptoms of Pinworm Infection?

The most common signs of a pinworm infection are itching around the anus and restless sleep. The itching is usually worse at night because the worms move to the area around the anus to lay their eggs. In girls, pinworm infection can spread to the vagina and cause a vaginal discharge. If the itching breaks the skin, it also could lead to a bacterial skin infection.

If your child has a pinworm infection, you can see worms in the anal region, especially if you look about 2 or 3 hours after your child has fallen asleep. You also might see the worms in the toilet after your child goes to the bathroom. They look like tiny pieces of white thread and are really small — about as long as a staple. You might also see them on your child’s underwear in the morning.

Belly pain and nausea are less common symptoms but can happen if there are many pinworms in the intestines.

How Are Pinworm Infections Diagnosed?

Your doctor may ask you to help make the diagnosis of pinworm by placing a sticky piece of clear cellophane tape against the skin around your child’s anus. Pinworm eggs will stick to the tape and can be seen under a microscope. The best time to do this is at night or in the morning before a bath (when there’s the most pinworm activity around the anus). The doctor also might take some samples from under a child’s fingernails to look for eggs.

How Are Pinworm Infections Treated?

If your child has a pinworm infection, the doctor will recommend an over-the-counter or prescription antiworm medicine. This is given in one dose and repeated in 2 weeks. The doctor may decide to treat the entire family, especially if your child has had a pinworm infection before.

Although medicine takes care of the worm infection, the itching may continue for about a week. So the doctor also might give your child a cream or other medicine to help stop the itching.

Regular hand washing and routine household cleaning (including frequent changing of underwear, and washing everyone’s pajamas, towels, and bed linens) also will help prevent the spread of a pinworm infection within the family.

Can Pinworm Infections Be Prevented?

Here are a few ways to prevent pinworm infections in your family:

  • Remind kids to wash their hands often, especially after using the toilet, after playing outside, and before eating.
  • Make sure your kids shower or bathe every day and change underwear and swimsuits daily.
  • Keep kids’ fingernails short and clean.
  • Tell kids not to scratch around their bottom or bite their nails.
  • Wash your kids’ pajamas every few days.

When Should I Call the Doctor?

Call the doctor if your child complains of itchy skin or always seems to be scratching the anal or vaginal area.

Also ask about whether pinworms could be to blame if your child has trouble sleeping or has begun to wet the bed. (Pinworms can irritate the urethra — the channel through which pee leaves the bladder and exits the body — and lead to bedwetting.)

Remember that pinworms are quite common among kids and aren’t harmful. By taking medicine and following some prevention tips, you’ll be rid of the worms in no time.

Reviewed by: Joanne Murren-Boezem, MD Date reviewed: July 2017

Pinworms: A-to-Z Guide from Diagnosis to Treatment to Prevention

Introduction to pinworms:

Although adults often shudder at the thought of pinworms, most kids don’t have this same gut response. In any case, pinworms are mostly harmless and inhabit people in every socioeconomic group and culture.

What are pinworms?

The pinworm, or Enterobius vermicularis, is one of the most common parasitic infections of humans. Somewhere between 10 percent and 40 percent of children have pinworms at any given time.
The adult pinworms are white and measure less than one-half inch long, with the diameter of a strand of thread. These tiny roundworms are quite complex. Like us, they have mouths, throats, and gastrointestinal tracts. Like us, they have nervous systems. The females have a vagina, a uterus, and ovaries. The males have a testicle, vas deferens, seminal vesicle, and ejaculatory duct. They eat, drink, pee, poop, and reproduce sexually.

The adult worms live in the colons (large intestines) of human children and apparently feed on human fecal matter.

When adult male and female worms copulate, each female pinworm produces about 10,000 fertilized eggs. At night, the pregnant female migrates from the colon, out through the child’s anus and onto the skin of the buttocks. There she violently expels all of her eggs and dies. Some of the eggs become airborne and land elsewhere in the child’s room, but the great majority of the fertilized eggs stay on the skin of the child’s buttocks. The eggs mature within six hours of being laid.

The adult worms and the eggs on the skin of the buttocks can cause intense itching in the child. When the sleeping child scratches, the eggs often get on the fingers and under the fingernails. If the child sucks his or her thumb or otherwise brings his or her hand to the mouth (perhaps while eating breakfast), the pinworm eggs are swallowed. They usually hatch within the small intestine and mature there. When they become adults, they move to the colon where they take up residence. The entire life cycle lasts four to six weeks.

Occasionally the story goes a little differently. Sometimes a child can inhale airborne eggs and become infected that way. Every now and then the eggs will hatch on the skin of the buttocks, and the immature larvae will crawl back through the anus, up into the rectum and eventually arrive in the colon. Also, the eggs can hatch on the skin of girls and the larvae crawl into the vagina instead of the rectum. This happens in up to 20% of girls with pinworms. The vaginal pinworms usually die out with no outside help.

Who gets pinworms?

Pinworms are found worldwide and can affect people of all ages, although the great majority of cases occur before age 12. Pinworms occur in all socioeconomic groups, but are more common wherever children are in close contact with each other.

What are the symptoms of pinworms?

Most children with pinworms have no symptoms at all. In the same way that many bacteria live in our intestines without making us sick, pinworms can live happily in our intestines without causing any problems. Since the pinworm almost always stays in the gastrointestinal tract (or vagina), there is usually no systemic illness.

Some children, however, develop nighttime itching of the skin around the anus. For a small number of these children, the itching can be quite intense.

The girls who develop vaginal pinworm infections often develop vaginal itching and sometimes a vaginal discharge.

Attempts to link pinworm infection to bed wetting or grinding of the teeth have been unsuccessful, but pinworm infestations can interfere with sleep.

Are pinworms contagious?

Pinworms are contagious. Fertile eggs are usually spread on fingernails, but can also be spread on clothing, bedding, or even house dust. Fertilized eggs can remain alive for 20 days, waiting to be swallowed or inhaled.

How long does pinworms last?

The life cycle of a pinworm is 4 to 6 weeks. Without treatment, infestation will continue as long as fresh eggs are being swallowed, unless a person develops immunity to pinworms, which is unusual before age 15.

How are pinworms diagnosed?

Stool and blood tests are not very helpful in diagnosing pinworms. Seeing a worm clinches the diagnosis. Check your child’s skin with a flashlight during the night and first thing in the morning. Look for white, wiggling threads. If it’s not wiggling, it’s probably just lint. Occasionally a wiggling worm will be seen on the surface of a stool. Pinworms are so common that children with nighttime anal itching are often treated without any lab test at all. The classic diagnostic tool is to apply a piece of transparent tape to the skin near the anus first thing in the morning. This tape can then be attached to a glass slide and examined under a microscope for the presence of eggs. Your doctor can supply you with a pinworm lab kit, if necessary. Remember, though, that these eggs are infective!

How are pinworms treated?

The treatment is two doses of an anti-pinworm drug. The second dose is given 2 weeks after the first.

Physicians disagree about whether or not to treat all family members. Treating the infected child alone will often get rid of the infestation. Anyone who sleeps with the child, or any family member or friend with itching should be treated. In stubborn cases, treating the family members, and particularly the other children can be a good idea.

Washing the bedding on the treatment day may help and is often recommended.

How can pinworms be prevented?

This easily transmissible infection is very common in children. It is not a sign of poor hygiene. It is easily spread at home, school, or daycare (pets have no part in the pinworm story). Since most kids experience no ill effects whatsoever, extreme measures to prevent pinworms are not wise.

I recommend trimming the fingernails, scrubbing the hands (after awakening, before meals – especially breakfast – and after toileting). These measures have never been proven to help at all, but they still seem like a good idea to me.

Where pinworms are a constant problem, treating every 3 months may help to prevent re-infestation.

Worms, Nematodes, Enterobiasis, Enterobius vermicularis


Pinworms are small parasites that can live in the colon and rectum. You get them when you swallow their eggs. The eggs hatch inside your intestines. While you sleep, the female pinworms leave the intestines through the anus and lay eggs on nearby skin.

Pinworms spread easily. When people who are infected touch their anus, the eggs attach to their fingertips. They can spread the eggs to others directly through their hands, or through contaminated clothing, bedding, food, or other articles. The eggs can live on household surfaces for up to 2 weeks.

The infection is more common in children. Many people have no symptoms at all. Some people feel itching around the anus or vagina. The itching may become intense, interfere with sleep, and make you irritable.

Your health care provider can diagnose pinworm infection by finding the eggs. A common way to collect the eggs is with a sticky piece of clear tape. Mild infections may not need treatment. If you do need medicine, everyone in the household should take it.

To prevent becoming infected or reinfected with pinworms,

  • Bathe after waking up
  • Wash your pajamas and bed sheets often
  • Wash your hands regularly, especially after using the bathroom or changing diapers
  • Change your underwear every day
  • Avoid nail biting
  • Avoid scratching the anal area

Department of Health

Pinworm Infection

Last Reviewed: October 2011

Pinworms are white, parasitic worms that can live in the large intestine of humans. They are about one-half inch long. While the infected person sleeps, female pinworms leave the intestinal tract and lay their eggs on the skin around the anus. The eggs are laid in a sticky, jelly-like substance that, along with the wriggling of the female pinworm, causes severe itching.

Who gets pinworm infection?

Pinworm is the most common worm infection in the United States. School-age children, followed by preschoolers, have the highest rates of infection. Cases of pinworm infection are seen most often at schools, daycare centers and other institutional settings.

What are the symptoms of a pinworm infection?

Pinworm infection may cause:

  • Itching around the anal area, difficulty sleeping and irritability.
  • If it is a severe infection, symptoms may include:
    • nervousness
    • restlessness
    • loss of appetite
    • weight loss
    • girls may experience vaginal itching and irritation (vaginitis), if pinworms are near the vagina.

How does someone get pinworms?

Pinworms are spread when an infected person, most often a child, has scratched his/her bare anal area and the eggs get under his/her fingernails. Pinworms can then be spread in the following ways:

  • By an infected child not washing hands after using the bathroom. If the child then touches playmates or toys, he/she may pass on the eggs.
  • Pinworm eggs can also be transferred to the fingers from clothing or bedding, and then spread around the home.
  • Eggs may be inhaled from the air or deposited onto food and swallowed.
  • Pinworms can survive up to two weeks on clothing, bedding or other objects, if kept at room temperature.

The eggs may hatch while still attached to the skin around the anus. They then move through the rectum to the lower intestine, where they grow to adult size within two to six weeks. Pinworm infections can be spread as long as either worms or eggs are present.

How is a diagnosis of pinworm infection made?

Finding the female worm or the eggs confirms the diagnosis of pinworms. To find a female worm:

  • At night, the adult worms can sometimes be seen directly around the anal area or in pajamas. The worm (one-quarter to one-half inch long) is clearly visible to the naked eye. Finding a worm confirms the diagnosis.
  • If adult worms are not visible, conduct a tape test in the morning. Apply a piece of transparent tape against the folds of skin around the anus to pick up any eggs or worms. Seal in a plastic bag.
  • Take the tape to a health care provider. The eggs and worms caught on the tape can be identified under a microscope.

Pinworms are rarely spotted in stool samples. Because bathing or a bowel movement can remove the eggs, the tape test should be done as soon as the person wakes up in the morning.

How is a pinworm infection treated?

Treating pinworms involves either prescription or over-the-counter drugs. Consult a health care provider before treating a suspected pinworm infection. Follow these treatment steps:

Step 1: Treat the infected person/any infected family members

  1. The infected person should take the medicine orally. It is given in two doses. The second dose should be given two weeks after the first.
  2. Bathe first thing in the morning to reduce egg contamination.
  3. Wash hands and under the fingernails thoroughly, after using the bathroom, before eating and after changing diapers.
  4. Discourage nail biting and scratching bare anal areas to avoid re-infection.
  5. Keep fingernails trimmed very short.
  6. Infection often occurs in more than one family member. Treat all infected family members at the same time.

Step 2: Treat the household

  1. Change and wash underwear and pajamas in hot water daily.
  2. Machine-wash sheets, blankets, towels and clothing in hot water to destroy eggs. Machine-dry at high temperature.
  3. Eggs are sensitive to sunlight, so open blinds in bedrooms in the daytime.
  4. 4. Since pinworm eggs are light and scatter easily, dust should be removed carefully from all surfaces in the home. Careful vacuuming or the use of an oiled cloth (which may be boiled or destroyed later) will help prevent the eggs from scattering.

How can pinworm infection and reinfection be prevented?

  • Wash hands and under fingernails frequently.
  • Encourage children to avoid scratching their bare anal areas.
  • • Pinworm eggs continue to be present (excreted) in the feces of an infected person for up to a week after the treatment, so precautions should be taken to prevent reinfection by washing hands thoroughly, especially under the nails.
  • Bathe daily.
  • Change and wash clothing and bedding frequently.

What if the pinworm infection occurs again?

If infection occurs again, consult your health care provider. In some cases, it may be necessary to treat the patient and close family contacts more than once.

For more information contact your local health department or go to the Centers for Disease Control and Prevention (CDC) website at

US Pharm. 2006;12:10-15.

Pharmacists who practiced in the 1970s may recall Povan, a red dye–derived medication once available for pinworm, and the seemingly endless number of prescriptions dispensed for it. This is in stark contrast to today’s practice–prescriptions for anthelmintics to treat pinworm are rare. However, that does not necessarily mean that the prevalence of pinworm has decreased; since public awareness of this ancient parasite has dropped, it is less likely to be recognized when it is present.

Prevalence of Enterobiasis
Infestation with pinworm ( Enterobius vermicularis) is known as enterobiasis. This is the most common helminth infestation in the United States, with an estimated 42 million infested, translating to 14% of the population.1,2 Investigators in other countries report much higher prevalences, such as 29% (Denmark), 39% (Thailand), 50% (England), and 61% (India).1

Causative Agent
E. vermicularis is a white nematode (roundworm) with a length of 8 to 13 mm for the adult female (about the length of a standard staple) and 2 to 5 mm for the adult male.3 Its width is about 0.5 mm.1 The ova are oval objects appearing microscopically to have three sides, approximately 55 x 25 mcm.1

Life Cycle/Transmission
Humans are thought to be the sole hosts of E. vermicularis (see sidebar).3,4 The common residence of the adult pinworm is the large intestine, where it attaches to the cecum and appendix.1 Following mating, the gravid female must lay as many as 16,000 eggs.1 They live for an average of eight to 13 weeks.1,3 Although the reproductive habits of pinworm may be unpleasant to contemplate, pinworms are equipped with the requisite instincts to ensure survival of their species. The gravid mother will not lay eggs inside the host, since the ability to spread throughout the population would then be impaired. Rather, the female E. vermicularis has evolved the strategy of exiting the anal opening to deposit the eggs in the folds of perianal skin–a process known as ovipositing. Following ovipositing, females reenter the anal opening. Successful reentry is termed retroinfection.1

Freshly laid Enterobius eggs are not immediately capable of infestation, as the larvae must develop first. The eggs embryonate (develop the ability to infest a patient) within four to six hours. 1,3 If the environment is moist, they are potentially capable of infestation for 20 days. The newly laid eggs are surrounded by a sticky, albuminous material that allows them to adhere to the anal opening. To guarantee survival of the species, these eggs must reach another human’s gastrointestinal tract, which can occur via several means.

An infested child might wear bed clothing that is sufficiently loose for the eggs to fall away as the host sleeps. If the eggs drop away at night, they could be found on sheets or blankets. The eggs are quite light and can be blown about by human activity, wind, or such activities as snapping egg-contaminated sheets while making the infested child’s bed. Inhaled eggs may not enter the lungs, due to their weight and size, but may be deposited in the oropharynx, where they are easily swallowed.2

A second method of spread can occur during the day following ovipositing. The eggs can be easily removed from the anal skinfolds by scratching; the child then has viable eggs on his or her fingers or under the nails. As the child plays during the day, the eggs may be deposited on surfaces that other children’s hands will have access to. Investigators visited homes and schools of infested children and identified pinworm eggs in 90% of samples taken from such diverse surfaces and locations as bars of soap, pet fur, swimming pools, walls of school dining rooms, and house dust samples. 5 If other children touching these surfaces subsequently place their fingers in their mouth to suck their thumb or bite their nails, the transmission loop is complete. Unfortunately, the child who originally had the infestation may also place his or her fingers inside the mouth, becoming reinfested and helping maintain a heavy parasite load–a process known as autoinfection.1

Clothing worn the next day might also be loose enough to allow the eggs to fall away and out of the clothing as the child plays and carries out routine activities. The eggs could deposit on carpets, floors, or playground equipment, or in a sandbox. Again, placing fingers in the mouth allows transmission to occur.

After the patient is infested, pinworms must hatch and mature before ovipositing begins. The average time from ingestion to detection of eggs in the perianal areas is four to six weeks.1

Pinworm infestation is linked to age, being most common in children of school age, followed by preschool children.6,7 Adults are the least common age-group to experience enterobiasis, with the exception of mothers whose children are infested.7

Children attending day care and other institutions are at greater risk for pinworm because of the high potential for transmission to those who are closely associated with the first case in the household. While some authors assert that pinworm crosses all social barriers, others state that poverty and poor personal hygiene increase the risk of infestation. 1,8,9

Symptoms may take weeks or even months to become noticeable after the eggs are ingested.1 While one third of those infested are asymptomatic, others begin to notice troubling vague and nonspecific symptoms.1,10 The most common is anal, perianal, and/or perineal pruritus, stimulated by movement of the female, and albuminous substance that surrounds the eggs.1,8,9,11 Itching worsens at night, when the female exits the anal opening.6 Other manifestations are anorexia, abdominal pain, irritability, disturbed sleep, insomnia, and restlessness.1,7

Ectopic Enterobiasis
Retroinfection via anal reentrance does not occur via an organized search by the parasite; rather, the parasite crawls blindly until a body orifice is detected. The search is not always successful, and pinworms may enter other orifices, a process known as ectopic enterobiasis. Ectopic enterobiasis is less common in males, as the urinary opening is in a more distant location from the anal opening. However, ectopic male infestation may cause urethritis or epididymitis. Female physiology favors ectopic enterobiasis, as the vaginal and urethral openings are in closer proximity to the anal opening. After pinworms have gained entrance to the female genitourinary tract, they may cause vaginitis, vulvar irritation, endometriosis, salpingitis, urethritis, pelvic inflammatory disease, or pyelitis.1,12 The patient may notice such symptoms as dysuria, enuresis, vaginal discharge, vulvovaginitis, or postmenopausal bleeding.1

Prevention of Enterobiasis
Parents of patients infested with pinworm may ask the pharmacist how to prevent a future problem and how to maintain cleanliness during an ongoing episode. Several commonsense steps can be followed to decrease the risk of reinfection. Most require added attention to hygiene.6,7 For instance, the patient should shower every morning to decrease the chance of spreading the parasite to others and of retroinfection. Showering is preferable to bathing, since soaking in the bath with eggs floating in the water could conceivably allow them to enter the genitourinary tract. Patients should be urged to change underwear and sleepwear each day and night. Each period of wear should be followed by thorough washing. While the CDC advises against the practice, sheets could be washed daily to remove eggs that fell onto them at night. If sheets are not washed every day, they should be pulled back, and all blinds and curtains should be opened during the day, as pinworm eggs are sensitive to sunlight. Nails should be trimmed short. Children and adults must strive to keep their fingers out of their mouths at all times. Hands must always be washed thoroughly after bowel movements, especially during a bout of enterobiasis. Hands should be washed before eating and after changing diapers. Children must be urged to stop scratching their anal area, to prevent contaminating their hands and to reduce their risk of excoriating the skin. Dressing them in close-fitting underwear and cotton gloves can reduce or stop nocturnal scratching. The floors should be vacuumed every other day, since eggs can survive for two weeks on the carpet. Children may be allowed to return to day care after the first treatment with pyrantel pamoate, if they have bathed and nails are trimmed and cleansed.

The patient leaflet describes steps to diagnose and treat enterobiasis. Patients may wish to provide a stool sample; however, pinworms are seldom found in stool specimens, as they are not usually released into the fecal stream.

The leaflet describes use of the only FDA-approved anthelmintic: pyrantel pamoate. The medication paralyzes the worm, causing it to lose its grip on the bowel lining and to be flushed from the body. Controversy surrounds the issue of FDA labeling versus recommendations from the CDC. The discrepancy stems from the fact that pyrantel pamoate is effective only for live worms and does not affect eggs or larvae. Thus, immature larvae and eggs that hatch after the first treatment remain fully viable and capable of beginning the infestation anew. The FDA-approved labeling states that the patient should take only one dose and take other doses only under the advice of a physician. However, the CDC states on a Web page devoted to patients: “With either prescription or over-the counter drugs. You should consult your health care provider before treating a suspected case of pinworm. Treatment involves a two-dose course. The second dose should be given 2 weeks after the first.”7 This statement to patients effectively countermands and invalidates the FDA-approved labeling and gives tacit approval to the pharmacist to recommend a second dose.

Pinworm is a common but seldom-recognized condition. An informed pharmacist can help infested patients obtain appropriate treatment and prevent spread to other family members and playmates.

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