Pinworm, or Enterobius vermicularis, is an itch-inducing parasite and the most prevalent worm infection in the U.S., affecting millions of children, of all socioeconomic backgrounds, each year. The Centers for Disease Control and Prevention (CDC) estimates that up to 50 percent of school-age children could be infected with pinworm at some point.

To keep you and your children safe from pinworm, it's best to take precautions. The most important: Wash your hands, especially after using the toilet or changing diapers, and before handling food. It’s the most effective way of preventing pinworm.

"As with so many infectious diseases, proper hand hygiene is the most important means of preventing the spread of infection," says Mary Anne Jackson, M.D., director of the Division of Infectious Diseases at Children’s Mercy Hospital in Kansas City, Missouri. "Proper handwashing includes using friction and rotary action for 15 seconds, including the palms, back of hands, wrists and fingernails."

Although the infection is most prevalent among children under 18, it’s easily spread to anyone in contact with or taking care of an infected child, making schools, family households, and daycare centers hot zones for pinworm.

The infection is spread through direct skin-to-skin contact or by touching contaminated surfaces such as clothing, bedding, toys, faucets, and toilet seats. Pinworm eggs can also be ingested or inhaled, for example, by touching your mouth or nose after coming in contact with a contaminated surface.

Once infected, tiny female pinworms lay microscopic eggs in the skin surrounding the anus. Some people infected with pinworms may experience no symptoms, while some experience anal or vaginal itching, which can result in irritability and sleeplessness. Severe cases of pinworm can cause weight loss (due to loss of appetite), urinary tract infections, and even appendicitis.

While the treatment for pinworm is effective, reinfection is common because eggs can live for two to three weeks, so repeating treatment after two weeks is recommended to rid your body of any eggs not killed by the first treatment.

"It’s important to keep in mind that you want to treat the child and all others in the family," says Jackson. "And then repeat treatment after two weeks."

In addition to medication and regular cleaning of common surfaces and diligent handwashing for the next two to three weeks, the CDC recommends following this hygiene checklist to reduce the spread of pinworm to other people in your home:

  • Don’t scratch. Scratching, especially near your anus, risks reinfection.
  • Mind your nails. Keeping fingernails trimmed means there’s less space for eggs to collect. Also, avoid nail biting.
  • Wash every day. Bathing, especially in the morning, can help remove a large amount of eggs—which pinworms lay while you sleep at night—from the skin.
  • Take showers, not baths. That’s because pinworms can potentially contaminate bath water.
  • Routinely change linens and underclothes. Also, laundering in hot water first thing in the morning can also prevent transmission and reinfection. Dry clothes on high heat.

Editor's Note: This article and related materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multistate settlement of consumer-fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).