An adult pinworm generally is 1/4 to 1/2 inch (about 6 to 13 millimeters) in length. The most common symptom of infection is anal itching, particularly at night, as worms migrate to the host's anal area to lay their eggs.
Pinworm infection is the most common type of intestinal worm infection in the United States and one of the most common worldwide. Pinworms are thin and white, measuring about 1/4 to 1/2 inch (about 6 to 13 millimeters) in length.
While the infected person sleeps, female pinworms lay thousands of eggs in the folds of skin surrounding the anus. Most people infected with pinworms have no symptoms, but some people experience anal itching and restless sleep.
Pinworm infection occurs most often in school-age children, and the tiny (microscopic) eggs are easily spread from child to child. Treatment involves oral drugs that kill the pinworms and thorough washing of pajamas, bedding and underwear. For best results, the entire family should be treated.
Symptoms of pinworm infection may include:
- Itching of the anal or vaginal area
- Insomnia, irritability, teeth grinding and restlessness
- Occasional stomach pain and nausea
Pinworms often cause no symptoms.
When to see a doctor
Consult your doctor if you have severe anal itching, especially at night.
Accidentally swallowing or breathing in pinworm eggs causes a pinworm infection. The tiny (microscopic) eggs can be carried to your mouth by contaminated food, drink or your fingers. Once swallowed, the eggs hatch in the intestines and mature into adult worms within a few weeks.
Female pinworms move to the anal area to lay their eggs, which often results in anal itching. When you scratch the itchy area, the eggs cling to your fingers and get under your fingernails. The eggs then get transferred to other surfaces, such as toys, bedding or toilet seats. The eggs can also be transferred from contaminated fingers to food, liquids, clothes or other people.
Pinworm eggs can survive for two to three weeks on surfaces.
Risk factors for pinworm infection include:
- Being young. Pinworm infections are most likely to occur in children ages 5 to 10. The tiny (microscopic) eggs are easily spread to family members, caregivers, or other children at school or child care centers. Pinworm infections are uncommon in children younger than age 2.
- Living in crowded spaces. People who live in institutions are at higher risk of developing pinworm infections.
Typical pinworm infections don't cause serious problems. In rare circumstances, heavy infestations can cause infection of female genitals.
The parasite can travel from the anal area up the vagina to the uterus, fallopian tubes and around the pelvic organs. This can cause problems such as inflammation of the vagina (vaginitis) and inflammation of the inner lining of the uterus (endometritis).
Although rare, other complications of a pinworm infection may include:
- Urinary tract infections
- Weight loss
- Infection of part of the abdomen (peritoneal cavity)
Pinworm eggs can cling to surfaces, including toys, faucets, bedding and toilet seats, for two weeks. So besides regular cleaning of surfaces, methods to help prevent the spread of pinworm eggs or to prevent reinfection include:
- Wash in the morning. Because pinworms lay their eggs at night, washing the anal area in the morning can help reduce the number of pinworm eggs on your body. Showering may help avoid possible re-contamination in bath water.
- Change underwear and bedding daily. This helps remove eggs.
- Launder in hot water. Wash bedsheets, pajamas, underwear, washcloths and towels in hot water to help kill pinworm eggs. Dry on high heat.
- Don't scratch. Avoid scratching the anal area. Trim your child's fingernails so there's less space for eggs to collect. Suggest that your child avoid biting his or her nails.
- Wash your hands. To reduce your risk of getting or spreading an infection, wash your hands well after using the toilet or changing a diaper and before eating.
Your doctor can confirm the presence of pinworms by identifying the worms or eggs.
To help your doctor make a diagnosis, you can perform the tape test. As soon as the person you suspect has pinworms wakes up and before he or she uses the toilet, washes or gets dressed, press the adhesive side of a piece of transparent tape to the skin around the anus. The eggs stick to the tape.
For best results, perform the tape test three days in a row, and then take the pieces of tape to your doctor. Your doctor can look at the tape under a microscope to see if there are any pinworm eggs.
To treat pinworm infection, your doctor may recommend over-the-counter pyrantel pamoate or prescribe medication to all members of your household to prevent infection and reinfection.
The most common prescription anti-parasite medications for pinworms are:
- Albendazole (Albenza)
You may have mild gastrointestinal side effects during the course of treatment, and you often need to take at least two doses to get rid of the pinworms completely.
Preparing for an appointment
What you can do
When you call to make an appointment, ask about performing the tape test. The test involves pressing the adhesive side of a piece of transparent tape to the skin around the anus of the person you suspect has pinworms as soon as the person awakens. The eggs stick to the tape.
You then take the tape to your appointment so the doctor can look for pinworms or eggs under a microscope.
Preparing a list of questions can help you make the most of your time with your doctor. For pinworm infection, some basic questions to ask include:
- If I don't have pinworm infection, what are other possible causes of my symptoms?
- If one family member has pinworms, does the whole family need to be treated?
- How do I rid my home of pinworms?
- How do I prevent reinfection?
What to expect from your doctor
Your doctor is likely to ask a number of questions during your appointment, including:
- When did the itching start?
- Does it occur mostly at night?
- Is there anything that makes the symptoms better or worse?
- Do other family members have similar symptoms?
- Do you know if you or your child has had contact with someone who has pinworms?
- Have you found any dead worms in pajamas, underwear or in the toilet?
What you can do in the meantime
If you have anal itching, try not to scratch.
Content Last Updated: June 16, 2020