Alopecia areata is a type of hair loss that usually affects hair follicles. It can occur in anyone, of any age and gender. It causes patchy hair loss, typically along the scalp, but it can also involve the eyebrows, eyelashes, and other body hair. In most cases, only small patches are affected and the hair will eventually regrow on its own. However, in some cases the hair loss can be more severe and widespread, involving large areas of the scalp or even all over the body.