Pinworm Infection

Written by Anna Giorgi | Published on August 15, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

Understanding Pinworms and Pinworm Infections

A pinworm infection is a type of human intestinal worm infection. Pinworms are tiny, narrow worms that are white and less than half an inch long. A pinworm infection, also known as enterobiasis or oxyuriasis, is the most common type of worm infection in humans in the United States. (CDC)

Pinworm infections are easily spread. They are most common in children between the ages of 5 and 10, people who live in institutions, and those who have regular, close contact with individuals in these groups. Pinworm infections can be effectively treated with medication, though reinfection is possible. Serious complications and long-term health effects are rare.

How Pinworm Infections Spread

Pinworms infections are highly contagious. You become infected with pinworms by unintentionally ingesting pinworm eggs, which have been deposited onto a surface by an infected person. The cycle of infection begins with the ingestion of these microscopic eggs.

Once the eggs enter your body, they remain in the intestine until they hatch and mature. As adults, the female pinworms move down the intestine, into the colon, and exit the body through the anus. The female pinworms lay eggs in the folds of skin around the anus. The presence of these eggs often causes itching and irritation.

When a person scratches the affected area, the pinworm eggs are transferred to the fingers. The eggs can survive for several hours on your hands. If the infected person touches bedding, clothing, toilet seats, toys, or other household objects, the eggs are transferred to these surfaces. Pinworm eggs can survive on these contaminated surfaces for up to three weeks.

The transfer of pinworm eggs is easier among children, who may put infected toys or other objects directly into their mouths. The eggs can also be transferred from contaminated fingers directly to food or liquids. Once you ingest these items, the eggs will spread to your intestine. While uncommon, it’s also possible for adults to inhale eggs that become airborne when bedding or clothing is shaken.

Risk Factors for Pinworm Infections

Pinworm infections affect people of all ages and geographical regions. Since the pinworm eggs are microscopic, it’s impossible to avoid infected individuals or areas.

While anyone can get a pinworm infection, the following groups are more susceptible:

  • children who attend daycare, preschool, or elementary school
  • family members or caregivers of infected children and adults
  • individuals who live in institutions or other crowded accommodations
  • children who don’t practice regular and careful hand washing prior to eating
  • children who have a habit of sucking their thumbs

Symptoms of Pinworm Infections

Some individuals with pinworm infections may not experience any symptoms. However, you may suspect that you or your child has a pinworm infection if you notice:

  • frequent and strong itching of the anal area
  • restless sleep due to the itching and discomfort
  • pain, rash, or other skin irritation around the anus
  • the presence of pinworms in the area of your child’s anus
  • the presence of pinworms in stools

Complications from Pinworm Infections

Most people don’t experience serious complications as a result of pinworm infections. Rarely, if the infestation is left untreated:

  • In females, pinworm infections can sometimes cause a urinary tract infection.
  • In females, pinworms can travel from the anus into the vagina, affecting the uterus, fallopian tubes, and other pelvic organs. Vaginitis, endometritis (an inflammation of the uterine lining), or other infections may result.
  • The presence of a significant number of pinworms can cause abdominal pain.
  • Substantial pinworm populations can rob your body of essential nutrients, which can cause weight loss.

Diagnosing Pinworm Infections

A tape test is the most reliable method for diagnosing a pinworm infection. A tape test consists of taking a piece of cellophane tape and pressing the sticky, adhesive side against the skin around the anus. Since pinworms often exit the anus while the infected person sleeps, you should conduct a tape test upon waking in the morning. If eggs are present, they will stick to the tape. Take the tape to your doctor, who can place it on a slide and examine it under a microscope to see if it contains pinworm eggs.

Routine morning activities, such as bathing or using the toilet, can remove eggs from your skin, so the results of a tape test are most accurate if the test is done when you first wake up. The Centers for Disease Control and Prevention (CDC) recommend that you conduct a tape test at least three times, on three consecutive mornings, to increase your likelihood of finding pinworm eggs if they are present.

Treating Pinworm Infections and Clearing Your Home of Worms

Medication

Most pinworm infections can be treated effectively with oral medication. Since pinworms can be passed so easily from one person to another, everyone living in the household of an infected person is usually treated at the same time to prevent reinfection. Caregivers and others who have close, personal contact with the individual are also treated.

The most common and effective medications to treat pinworm infection are:

  • mebendazole
  • albendazole
  • pyrantel pamoate

One course of medication usually involves an initial dose, followed by a second dose two to three weeks later. More than one course may be necessary to fully eliminate the pinworm eggs. Creams or ointments can be used to soothe itching skin in the area around the anus.

Clearing Your Home of Pinworms

In addition to medication, a specific regimen of hygiene and household cleaning can help you completely eliminate the pinworm eggs:

  • Ensure that the infected person and other household members practice thorough hand washing with warm water and soap, especially before eating.
  • Encourage everyone in the household to shower and change their underwear every morning.
  • Clean everyone’s fingernails and cut them short.
  • Instruct the infected person and others to stop biting their nails.
  • Tell the infected person to refrain from scratching the anal area.
  • Use hot water to launder all bedding, towels, washcloths, and clothing in the affected house. Dry these items using high heat.
  • Avoid shaking clothing and bedding to keep pinworm eggs from spreading into the air.
  • Do not allow children to bathe together to prevent spreading pinworm eggs in the bath water.
  • Thoroughly clean any surfaces that may be infected, including toys, floors, countertops, and toilet seats.
  • Carefully vacuum all carpeted areas.

Humans are the only pinworm hosts. Your cat or dog is unable to infect you or be infected with pinworms, so it is not necessary to treat your pets for the infection.

Outlook for Pinworm Infections

It’s possible to eradicate a pinworm infection with medication and the recommended cleaning regimen. However, because pinworm eggs are invisible to the naked eye and are highly contagious, reinfection can easily occur. A person can reinfect themselves or become reinfected by eggs from another person. If you experience recurrent infections after you have treated your household, individuals and locations outside the household may be the primary source of the pinworm eggs.

Tips to Prevent Pinworm Infections

The best way to prevent pinworm infections and reinfections is to follow recommended hygiene routines and encourage other household members, especially children, to do the same. You can work to prevent pinworm infections with the following practices:

  • Wash your hands with warm water and soap after using the toilet. Be especially careful after bowel movements and changing diapers. Do the same before preparing food and eating.
  • Keep your fingernails short and clean.
  • Discourage children’s habits such as nail biting or scratching that could spread pinworm eggs.
  • Shower daily in the morning to remove pinworm eggs that may have been deposited overnight.
  • Change your underwear and clothing daily.
  • Use hot water in the washing machine, followed by a hot dryer, to launder bedding, clothing, and towels that may contain pinworm eggs.
  • Keep rooms well lit during the day because the eggs are sensitive to sunlight.
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