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 microscopic eggs are easily spread from child to child. Treatment involves oral drugs that kill the pinworms and thorough washing of pajamas, bed linens 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 and restlessness
- Intermittent abdominal 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 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, bed linens 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 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
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 recontamination in bath water.
- Change underwear and bed linen daily. This helps remove eggs.
- Launder in hot water. Wash bedsheets, nightclothes, 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. Discourage nail biting.
- Wash your hands. To reduce your risk of getting or spreading an infection, wash your hands thoroughly after having a bowel movement or changing a diaper and before eating.