Pinworms are common among preschool and elementary age children. Itching around the rectum at night is usually the first, and possibly only, symptom. To check for pinworms in your child, wait for one hour after your child has been asleep. Take a flashlight into the dark room and check the rectal area. You should see small, thread-like worms that are approximately ¼ inch long. If you see pinworms, call the office to speak with the nurse for further instructions.