What Are Pinworms? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Pinworms (Enterobius vermicularis) are teeny, white, threadlike roundworms that infect the intestines of humans. These parasites hatch in the small intestine, then move on to the large intestine where they reside for about one or two months. After that timeframe, female pinworms crawl downward and out of the anus for the sole purpose of laying thousands of microscopic eggs. These eggs remain viable for one to two weeks. (1,2)

It’s estimated that anywhere from 20 to 42 million people in the United States, commonly children, have had a pinworm infection. While irritating, and perhaps embarrassing, a pinworm infection is generally considered harmless. (3)

Many people with a pinworm infection don’t exhibit any symptoms. But generally speaking, when infected individuals do experience symptoms, it happens once the worms have relocated to the skin surrounding the anus to lay their eggs. Here, a sticky substance around the eggs can often irritate the skin, causing anal itching, (3) which is the primary symptom of a pinworm infection. Other symptoms may include:

• Worms Present in Feces This is common, according to the National Organization for Rare Disorders. (4)
• Difficulty Sleeping Pinworms move to the area around the anus at night in order to lay eggs, which can induce itching that disturbs sleep.
• Vaginal Itching
• Vaginal Discharge (1)
• Nausea and Vomiting These are rarely reported.
• Bed Wetting This is a rare symptom.
• Stomach Pain This is also rare. (4)

Quite simply, one gets a pinworm infection after ingesting worm eggs. To become infected, an individual either directly (via their hands or fingernails) or indirectly (via contaminated clothing, toilet seats, bedding, toys, or food, for example) transfers pinworm eggs from the anus to their mouth. In addition, because pinworm eggs are so teeny, they can become airborne, where they are inhaled and ingested. While pinworm infections affect people of all ages and socioeconomic background, according to the Centers for Disease Control and Prevention (CDC) those who are most impacted include:

• School-age and preschool-age children
• Institutionalized individuals
• Those who share a household with infected individuals
• Individuals who are caregivers to the infected (5)

The eggs laid on the skin surrounding the anus can survive for up to three weeks, which allows plenty of time for the infected person to scratch the area, have the eggs become embedded under the fingernails, and inadvertently reinfect themselves, thus continuing the parasites’ lifecycle. (4)

There are three different ways to approach the diagnosis of pinworms.

Examine the anus. Wake your child about one to two hours after you put him or her to bed, then check around his or her anus for wiggly, white, hair-thin worms that are about ¼ to ½ inch (0.63 to 1.27 centimeters) long. (3,6)

Use transparent tape. First thing in the morning (before your child bathes or uses the bathroom), firmly place a 1-inch piece of transparent tape against the skin around the anus for a few seconds, allowing any pinworm eggs to stick to the tape. Next, transfer the tape to a glass slide, sticky side down, and place inside a sealed plastic bag. Repeat for three consecutive mornings and take the tape to the doctor for microscopic examination. If you see worms that have adhered to the tape, you can likely inform your doctor that you’ve found pinworms. (7)

Analyze under-the-fingernail samples. A physician may also opt to use a microscope to examine a specimen taken from under a child’s fingernails. Eggs may be found there due to scratching. (8)

Because pinworm eggs can live for one to two weeks, it’s important to follow the initial treatment with a second dose in two weeks’ time. After taking the medication, itching should stop in five to seven days. (9)

With proper hygiene, a pinworm infection is usually considered self-limiting, which means it can resolve on its own with no long-term ill effect. (4) But most people would rather be sure the infection is gone and opt for treatment. Your healthcare provider will likely recommend that all members of your household get treated in order to prevent infection and reinfection, including those who don’t exhibit symptoms. (10) Treatments include the following:

Medication Options for Pinworms

One of the following is usually the treatment of choice. No matter which is used, an initial dose is given, followed by a second dose two weeks later to prevent reinfection by worms hatched from eggs not killed the first go-round.

• Prescription The drugs mebendazole (Emverm) and albendazole (Albenza) are oral meds that cause pinworms to be expelled through bowel movements. (3) They’re generally not recommended for use in children under 2 years old. (6)
• Over-the Counter (OTC) While pyrantel (Pin-Away) and Reese’s Pinworm Medicine (pyrantel pamoate) are available without prescription, they’re considered less effective than the other choices. (11)

Alternative and Complementary Therapies

Adhering to stringent hygiene measures for six weeks, which is the lifespan of a pinworm, can clear up an infection without medication. These practices also reduce the risk of reinfection. If any member of your household is a nail-biter or thumb-sucker, this method is likely not right for you. (12) These med-free measures include:

• Keep fingernails short.
• Scrub fingernails with a nail brush daily.
• Wash hands thoroughly for at least 20 seconds after using the bathroom and before eating.
• Shower each morning to help remove eggs from the skin.
• Don’t share towels or washcloths.
• Wear snug underwear, avoiding boxer shorts.
• Change underwear every morning.
• Wash bed linens, pajamas, towels, and washcloths with each use; do not shake before laundering.
• Change hand towels daily.
• Vacuum carpets and clean floors at least once a week, paying special attention to the bedrooms and bathrooms.
• Clean kitchen and bathroom surfaces daily, especially faucets and the toilet flusher.
• Refrain from eating in the bedroom to avoid possibly swallowing eggs that have landed in bed linens.
• Keep toothbrushes in a closed cabinet. (Theoretically, airborne eggs can land on toothbrushes.) (12)

While it’s difficult to prevent pinworms, good hygiene goes a long way. It’s a good idea to practice the following:

• Always wash hands with soap and warm water for at least 20 seconds after using the bathroom or changing diapers, and prior to handling food.
• Frequently wash underwear, pajamas, bedding, and toys.
• Regularly vacuum.
• For adults, avoid of oral-anal contact during sexual relations. (3)
• Change underwear and bathing suits daily.
• Keep fingernails short and clean.
• Refrain from biting fingernails.
• Avoid scratching one’s rear end. (1)

Pinworm infections usually don’t cause any serious issues. However, there is the possibility of a secondary bacterial infection, which can occur when a lot of irritation and scratching of the anal area causes the skin to break. (13)

Other complications are rare but can include:

Vaginitis The vagina can become inflamed if a heavy infestation of worms travel from the anal area to the vagina.

Endometritis This occurs when pinworms move from the vagina into the uterus, fallopian tubes, and around the pelvic organs, causing inflammation of the inner lining of the uterus. (2)

Urinary Tract Infections (UTIs) UTIs may occur in some cases.

Weight Loss Loss of weight is a rare but possible complication. (2)

Peritonitis With this complication, inflammation occurs in the peritoneum, which is the tissue that lines the abdominal wall and covers most of the organs in the abdomen, according to research from 2015. (14)

Appendicitis Appendicitis is another potential secondary infection. (4)

More than one billion people worldwide are thought to be infected with pinworms. (3)

It’s estimated that anywhere from 20 to 42 million people in the United States have had a pinworm infection; about 50 percent of people under 18 years old, those who care for infected children, and individuals who are institutionalized have had a pinworm infection, according to the CDC. (5)

Parasitic worms known as soil-transmitted helminths (STH) are passed to the soil through the feces and may remain in the soil for months or years. They are responsible for a lion’s share of the parasitic disease burden worldwide. (15) Symptoms of an infection by these parasites can be similar to those of pinworms.

Ascaris These parasitic worms are found in tropical areas and can cause either no symptoms, or symptoms such as fever, cough, wheezing, stomach cramps, vomiting, and restless sleep. (16) Infection occurs when eggs are ingested after putting contaminated hands or fingers in one’s mouth — or by consuming produce that’s come in contact with contaminated soil and not properly cooked, washed, or peeled. (15)

Hookworm Infections are most commonly found in temperate and warm, moist climates. The worms penetrate the skin when a person walks barefoot on contaminated soil and then travel to the small intestine, where they can cause abdominal pain and sometimes anemia. (4) People in good health may not exhibit any symptoms. (16)

Whipworm Hot, humid climates are generally where whipworms are found. Like ascaris, whipworm infections occur when eggs are ingested via hand-to-mouth action or after consuming contaminated fruits or vegetables. Usually, there are no symptoms, but a severe infection can bring about mucousy, watery, and bloody bowel movements and the frequent and painful passage of stool. Rectal prolapse (part of the large intestine slips outside of the anus) can also occur. (17)

Centers for Disease Control and Prevention (CDC)

The CDC is always a reliable go-to for research-based information. And beyond all the scientific names and the epidemiologic facts, the CDC also offers user-friendly info, like the very helpful Pinworm Infection FAQ section, which tackles topics such as swimming while infected with pinworms, whether pets can give you pinworms, and more.

KidsHealth

This nonprofit children’s health system provides readers with easy-to-understand info on a wide variety of health topics. The best part: You can find guidance on the very same topic written specifically for parents, for kids, and for teens. With pinworms, for instance, kids can learn about what’s making their rear end itchy in a friendly, kid-appropriate way. Meanwhile, parents can read more about the nitty-gritty.

HealthyChildren.org

This website is from the American Academy of Pediatrics, a professional organization that boasts roughly 67,000 pediatricians as members. The group is a leading national voice on children’s health, supporting research, science, and presenting the info in a user-friendly manner on its HealthyChildren.org website. Here, parents can find info on anal itching and pinworm infections. Plus, there’s an exceedingly helpful Symptom Checker, where parents can plug in various ills and injuries to get specific help.