Hair loss.

Alopecia is partial or total loss of hair as a result of any number of causes, including the normal aging process. In children, alopecia may be a reaction to a drug or therapy (such as chemotherapy or radiation therapy), or may result from a skin disorder or hormone imbalance. When hair is lost in patches for unknown causes, the condition is termed alopecia areata. When bald spots are the result of compulsive hair-pulling, the condition is termed trichotillomania.