Answer:
A pinworm is a little white worm. They grow to the maximum of one inch. People normally get pinworms by inhaling a microscopic egg that travel down to your digestive system and hatches into a larvae. The larvae then travels to the small intestine. From there, it matures into an adult and travels to and through the large intestine. While sleeping, these worms can crawl out of your butt and will lay eggs around the anal area. This will cause the area to become VERY itchy. Pinworms do irritate you, but are not fatal and can not cause you any harm. Go to a doctor and get tested for worms. if positive, he will put you on medication to get rid of these parasites.
(i have pinworms and they ITCH!)