What is a pinworm?

A pinworm is a small, white, roundworm that can live in the intestines of humans and other animals. Pinworms are very common, especially in children. Female pinworms lay eggs around the anus, which can cause intense itching. Children who have pinworms may scratch their anus, which can lead to a bacterial infection. Pinworms are generally not harmful, but they can be very uncomfortable.