Baldness, or alopecia, lack or loss of hair, usually from the scalp, due to disease of hair follicles. Pattern baldness is an inherited tendency, often starting when a man is in his 20s. It is found in about 40% of the male population. Alopecia areata is a disease of unknown cause producing usually temporary patchy baldness, though it may be total. Prolonged fever, lupus erythematosus, ringworm, certain drugs, and poisons may lead to temporary baldness.