Gray hair
Gray hair color typically occurs naturally as people age, usually turning their hair from its natural color to gray and then to white. More than 40 percent of Americans have some gray hair by their fortieth birthday, 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 it is passed down genetically. Many people use hair dye to disguise the amount of gray in their hair.
The change in hair color is caused by the gradual decrease of pigmentation that occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. Two genes appear to be responsible for the process of graying, Bcl2 and Mitf. 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.[1]
In some cases, gray hair may be a deficiency of B12 or caused from a thyroid imbalance.[2]
References
- ↑ Nishimura EK, Granter SR, Fisher DE (2005). "Mechanisms of hair graying: Incomplete melanocyte stem cell maintenance in the niche". Science. 307 (5710): 720–4. PMID 15618488.
- ↑ http://www.paralumun.com/hairg.htm