Loss of hair in sharply defined patches usually involving the scalp or beard.

A patch baldness that typically begins with rapid hair loss on certain areas of the scalp and sometimes it progresses to complete baldness and even loss of body hair.

Alopecia areata affects both males and females and, most often, children and young adults. It seems to be caused by the body's own immune system which attacks the hair follicles and disrupts normal hair formation.

The hair can sometimes regrow within a year without treatment; however, the longer the period of hair loss, the less chance that it will regrow.