Alopecia

Loss or absence of hair, which may occur at any hair-bearing site on the body but which is usually noticeable only on the scalp. Male-pattern baldness, the most common form of alopecia, is hereditary and most often affects men. Normal hair is lost initially from the temples and crown and is replaced by fine, downy hair; the affected area gradually widens. Other hereditary forms are rare. They may be due to an absence of hair roots or abnormalities of the hair shaft. In generalized alopecia, the hair falls out in large amounts. Causes include various forms of stress, such as surgery, prolonged illness, or childbirth. Many anticancer drugs cause temporary alopecia. The hair regrows when the underlying cause is corrected. Localized alopecia may be due to permanent skin damage (for example, by burns or radiotherapy) or trauma to the hair roots by styling or, rarely, trichotillomania (a disorder in which sufferers pull out their hair). The most common type of localized hair loss is alopecia areata, which is an autoimmune disorder. There is no specific treatment, but the hair usually regrows within a few months. Alopecia universalis is a rare, permanent form of alopecia areata that causes loss of all the hair on the scalp and body, including the eyelashes and eyebrows. Skin diseases such as scalp ringworm (see tinea), lichen planus, lupus erythematosus, and skin tumours may also cause localized hair loss. Treatments for male-pattern baldness include hair transplants or drug treatments with minoxidil or finasteride.