Hair

"Hair is the crowning glory"—this old double-play of words emphasizes the significance of hair for men and women. From a physiological point of view, hair provides mechanical protection, insulation, and a wick effect for the dispersal of lubricating sebum and sweat over the adjacent skin. The personalization of hair as a means of defining individual (or group) identity is of equally importance in many societies. It has fundamental social and cultural significance for the individual.

The number of active follicles declines by 30 to 50 percent between the ages of thirty and fifty. This is associated with a decline of male-type hormonal substances. The hair becomes sparser and the sebaceous (grease) gland enlarges. The gland output is reduced by as much as 30 percent in women, but this is more variable and sometimes increased in men.