Alopecia or hair loss is the meical description of the loss of hair from the head or body, sometimes to the extent of baldness. Unlike the common cosmetic depilation of body hair, alopecia tends to be involuntary and unwelcome, e.g., androgenetic alopecia. However, it may also be caused by a psychological compulsion to pull out one's own hair (trichotillomania) or the unforeseen consequences of voluntary hairstyling routines (mechanical "traction alopecia" from excessively tight ponytails or braids, or burns to the scalp from caustic hair relaxer solutions or hot hair irons).