Symptoms of pinworm infection may include:

• Itching of the anal or vaginal area
• Insomnia, irritability and restlessness
• Intermittent abdominal pain and nausea

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.

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