Lack or loss of hair, either permanent (from destruction of hair follicles) or temporary (from short-term follicle damage). Male pattern baldness is inherited and affects up to 40percnt of men; treatments are transplanting of follicles from areas where hair still grows and application of drugs (e.g., minoxidil) to the scalp. Other causes of permanent baldness are skin diseases and injuries, inborn lack of hair development, and severe follicle injury. Temporary hair loss may follow high fever or come from X rays, drugs, malnutrition, or endocrine disorders. Alopecia areata, with sharply outlined patches of sudden complete baldness, is also usually temporary.

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