Hair loss or baldness is a loss of hair from the head or body. Baldness can refer to general hair loss or male pattern baldness specifically. Some types of baldness can be caused by alopecia areata, an autoimmune disorder. The extreme forms of alopecia areata are alopecia totalis, which involves the loss of all head hair, and alopecia universalis, which involves the loss of all hair from the head and the body.
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