baldness, thinning or loss of hair as a result of illness, functional disorder, or hereditary disposition; also known as alopecia. Male pattern baldness, a genetic trait, is the most common cause of baldness among white males. It is carried by females, but they are rarely susceptible inasmuch as it develops under the influence of testosterone, a male sex hormone; women, however, may experience an overall thinning of the hair. Hair loss begins at the forehead and crown and is slowly progressive. Male pattern baldness may be cosmetically disguised by hair-follicle transplants. Drug treatments with minoxidil (Rogaine) or finasteride (Propecia) have been used with limited effectiveness.
Diseases characterized by high fever (e.g., scarlet and typhoid fevers), malnutrition, chemotherapy, and glandular disorders can all cause balding. Treatment of the disease or dysfunction will usually halt the loss of hair, and if the scalp and hair follicles are not severely damaged, hair will usually regrow spontaneously. Scalp infection, oiliness or dirtiness of the scalp and hair, and excessive teasing and lacquering of hair are also conducive to baldness. Alopecia areata is a disease of unknown origin characterized by noninflamed bald patches in the scalp hair and beard. It is recurrent but is usually of short duration.