Effects of aging on hair color: Children born with a certain color may find that it gradually darkens as they grow. Many blond, strawberry blond, light brown, or red haired infants experience this. A change in hair color typically occurs naturally as people age, usually turning their hair to gray and then white. More than 40 percent of Americans have some gray hair by age 40, but white hairs can appear as early as childhood. The age at which graying begins seems to be almost entirely based on genetics. Sometimes people are born with gray hair because they inherit the trait genetically. Some people use hair dye to disguise the amount of gray in their hair.
Two genes appear to be responsible for the process of graying, Bcl2 and Bcl-w. The change in hair color is caused when melanin ceases to be produced in the hair root and new hairs grow in without pigment. The stem cells at the base of hair follicles are responsible for producing melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying.
 Other medical conditions affecting hair color
Albinism is a genetic abnormality in which no pigment is found in human hair, eyes or skin. This results in gray, blue, or red eyes. The skin is pale and the hair is white or pale blond.
Vitiligo is a patchy loss of hair and skin color that may occur as the result of an auto-immune disease.
Malnutrition is also known to cause hair to become lighter, thinner, and more brittle. Dark hair may thus turn reddish or blondish due to the decreased production of melanin. The condition is reversible with proper nutrition.
Werner syndrome and pernicious anemia can also cause premature graying.
A recent study demonstrated that people 50-70 years of age with dark eyebrows but gray hair are significantly more likely to have type II diabetes than those with both gray eyebrows and hair.
 Artificial factors affecting hair color
A 1996 British Medical Journal study conducted by J.G. Mosley, MD found that tobacco smoking may cause premature graying. Smokers were found to be four times more likely to begin graying prematurely, compared to nonsmokers in the study.
Gray hair may temporarily darken after inflammatory processes, after electron-beam-induced alopecia, and after some chemotherapy regimens. Much remains to be learned about the physiology of human graying.
68 mths ago