Overview of Pinworm Infection

Dealing with itchy bottoms and sleepless nights

Mother with her toddler on the potty
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Pinworm infection (known clinically as enterobiasis vermicularis or oxyuriasis), is itchy and unpleasant, but it is not a serious health threat. According to the Centers for Disease Control and Prevention (CDC), pinworm infection is the most common worm infection in the United States.

This infection causes severe itching in the rectal area. It mostly affects preschoolers and school-aged children, but adults can get it too. It is highly contagious and affects people who live in close, crowded quarters or who live in the same house with someone who has pinworm.

Enterobiasis is diagnosed based on the symptoms or when the egg or the worm itself is seen, and it can be treated with prescription or over-the-counter (OTC) medication.

Symptoms

Pinworm commonly causes itching, typically in the rectal area. It affects males and females. Pinworms can cause vaginal itching and discharge in girls and women. It's usually worse at night and the itching sensation can be irritating enough to interfere with sleep.

Adults and children who have pinworm may spend a long time in the shower or pool because the water can feel soothing or due to an urge to clean the itchy area.

Bedwetting is another possible symptom of enterobiasis, especially among young children who have recently learned to control their bladder at night. This occurs because the worms can irritate the urethra—the thin tube by which urine leaves the bladder and passes out of the body.

Complications

Children and adults who develop a pinworm infection may scratch the irritated area, This can cause swelling, redness, and bleeding. Skin wounds from scratching can become infected with bacteria, resulting in a condition called perianal cellulitis.

Sometimes, pinworms cause digestive symptoms such as abdominal pain or nausea. Weight loss can occur due to loss of appetite if stomachaches persist. Pinworms are parasites, which means they can leech essential nutrients from the body, resulting in malnutrition.

Sometimes pinworms can spread to the female reproductive tract, leading to complications such as urinary tract infections, vaginitis, and even endometriosis.

Causes

Pinworm discomfort and itching are caused by the presence of Enterobius vermicularis parasite eggs near the rectum. These eggs are tiny and can only be seen with a microscope.

Pinworm is a contagious infection that is transmitted by touching an infected surface, and then putting your hands (with the parasite eggs on them) in your mouth or nose. If you get the eggs on your hands, you can also transmit the infection back to yourself or to others by touching food, drink, eating utensils, surfaces, or fabrics. You can also breathe in the eggs because they are so small.

The eggs can survive anywhere—bed linens, towels, clothing, toilets, bathroom fixtures, toys and sandboxes, kitchen counters and utensils, classroom desks, and school lunch tables. They do not, however, live on animals, so you can't get pinworms from your dog or cat (or pass the parasite along to a pet if you're infected). 

Note that pinworm eggs can live on surfaces outside of the body for as long as two to three weeks.

Pinworm In the Body

The Enterobius vermicularis parasites, sometimes called threadworms or seatworms, are small, and thin. They belong to a category of parasites described as nematodes or roundworms.

Once the eggs are inside the body, they travel to the small intestine to hatch; the larvae then move on to the large intestine where they live as parasites while maturing. After a month or two, adult female pinworms take yet another trip, this time to the area around the rectum, to lay eggs and then die. The total lifespan of a pinworm is about 13 weeks.

Despite being too tiny to be seen, the eggs trigger tremendous itching in the perianal area. You can get the eggs on your hands and underneath your fingernails by scratching the egg-infested area. Putting your hands near your mouth and nose can set off a new pinworm lifecycle.

Diagnosis

Pinworm is usually diagnosed based on the symptoms. The diagnosis can be confirmed by identifying the eggs or the worms themselves. The eggs, which are found near the rectum, under the nails, or on clothes or other fabrics, are too small to see. They can be identified based on a microscopic examination.

Tape Test

Another way to check for pinworms is with a tape test, which can be used to collect pinworm eggs for microscopic examination. Your doctor may give you the materials for this test. The worms tend to lay eggs at night, so the morning is the best time to collect them.

Here are the steps for a pinworm tape test:

  1. In the morning, before bathing, press the sticky side of an inch-long piece of clear tape against the anal area. Hold it there for a few seconds to give the eggs time to adhere firmly to the tape. 
  2. Transfer the tape sticky-side down to a glass slide, place the slide in a clean plastic bag. Seal the bag and wash your hands.
  3. You can repeat the test on three separate days to increase the chance of picking up the eggs.
  4. Take the slides to your doctor for an examination.

Live worms may be seen near the rectum or on clothes. They look like thin white threads, and they might or might not be alive and moving.

Treatment and Prevention

There are several prescription medications for treating pinworm infection, such as Emverm (mebendazole) and Albenza (albendazole). OTC pyrantel pamoate, which comes as a liquid, and is safe for kids ages 2 and up. You also can sometimes find this medication sold under a drugstore brand, such as CVS.

These medications are taken in two doses. The second dose is taken two weeks after the first dose. Your doctor may recommend that family members get treated as well.

In addition to using medication to get rid of pinworm infection, there are measures you should take to prevent it from spreading. These include:

  • Cutting an infected child's nails very short to avoid getting the eggs under the nails and scraping open the skin when scratching
  • Making sure everyone in the household washes their hands frequently with warm, soapy water
  • Washing all clothing, bed linens, and towels that might have had contact with the pinworms in hot water
  • Don't shake fabric items out before they've been washed
  • Wiping down any surfaces or items such as toys that could be harboring pinworm eggs.
  • Vacuuming all carpets
  • Keeping rooms well-lit during the day, as pinworm eggs are sensitive to light
  • Bathing children separately and daily
  • Washing kids' pajamas every few days and putting clean underwear on them every day

It may take a little time and effort, but by following these strategies you should be able to get your household free of pinworms within a few weeks.

A Word From Verywell

Pinworm is relatively common, especially among children. If you or your child or another loved one (such as a parent with chronic illness) develops pinworm, there is no need for alarm. It does not reflect on your cleanliness or hygiene. This is simply an infection that happens to be present in most communities—and spreads through regular day-to-day contact with other people.

People do not frequently discuss pinworm infection—so it can be hard to know whether you got it from your work or from a public place, or whether a family member brought it home. Routine handwashing with soap, especially before touching food or your mouth, is the best way to prevent re-infection.

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