Pinworm infections in children usually occur when a child swallows pinworm eggs, according to WebMD. The eggs then travel to the child's intestinal tract, hatching out into worms in around 1 month. The worms crawl out of the child's rectum at night, laying eggs around the anus.
The eggs cause itching, and a child can carry the eggs on his fingers and under his fingernails after scratching, notes WebMD. The eggs stick to items the child touches and are able to live outside the body for up to 3 weeks. Adults and other children coming into contact with the items touched by the child can get the eggs on their hands and may ingest the eggs if they touch their mouths or food.
Pinworms spread in this way throughout homes, schools and daycare centers, advises WebMD. For this reason, people who are often together usually spread the pinworms to one another. An additional mode of transmission is inhalation of airborne eggs, although it is a more rare instance. Pinworms are also transmissible via water in the swimming pool.
Symptoms of pinworms include anal itching and sleeping restlessly due to the itching. Pinworm infections do not often cause serious health issues.