Factors such as light, hormones , temperature, and nutrition affect the rate of hair growth and the strength of the hair. The lengths of the phases in the hair life cycle also vary in different parts of the body. For example, scalp hair has the longest growth phase, and grows about 0.35 mm each day. Hair Color Melanocytes are pigment-producing cells. They are located throughout the body, and give skin including freckles and age spots and hair their color.
Melanocytes produce pigments in the form of melanin granules.
The melanoctye cells then transport the granules into other, surrounding kerainocyte cells. The hair shaft gets its color from melanin of melanocytes at the base of the hair follicle. Keratinocytes then differentiate, die and are pushed upward to become the protruding hair shaft. Eumelanin is present in hair that is brown, brownish-black, or black. White or gray hair color occurs when the pigment-producing cells no longer produce melanin or the melanocytes are absent.