Greying hair is one of the most obvious indicators of aging, but is quite easily camouflaged by coloring the hair. Although grey is the color most often associated with aging, darkening of the hair is also a subtle indicator, particularly for people with fair hair. It is seldom that a blonde child retains a white head of hair throughout life. For this reason, many fair haired' individuals bleach and color their hair as they get older; they wish to retain the hair color of their youth

With age, pigment cells throughout the skin and hair are lost. Hence the new hair growth is grey. The oft heard comment "I am going grey", reflects this gradual process. With advancing age, the grey hair is eventually replaced by hair which is totally deplete of pigment cells and is white in color.

Whether or not hair turns grey, and to what extent, is generally determined by hereditary factors. There are some rare conditions in which the body perceives the pigment cells in the hair as foreign and attacks them, resulting in loss of color unexpectedly at an early age. This can sometimes be brought on rapidly after a period of great stress, such as a terrible tragedy.