As in many animals, human hair has a function as sensory organ and the physiological function of protecting the skin from environmental influences such as ultraviolet ray or temperature change (Figure).

In addition, humans are social animals and perceive individual, distinguishing characteristics of personality or youth to be expressed by scalp hair, eyebrow, mustache, and other bodily hair (Figure).

Hair has the above properties, including thickness, length, quality, color, density according to the area where the hair grows.