Why does hair turn gray?
November 23rd 2011 13:56
The pigment in hair, as well as in the skin, is called melanin. There are two types of melanin: eumelanin, which is dark brown or black, and pheomelanin, which is reddish yellow. Both are made by a type of cell called a melanocyte that resides in the hair bulb and along the bottom of the outer layer of skin, or epidermis. The melanocytes pass this pigment to adjoining epidermal cells called keratinocytes, which produce the protein keratin?hair's chief component. When the keratinocytes undergo their scheduled death, they retain the melanin. Thus, the pigment that is visible in the hair and in the skin lies in these dead keratinocyte bodies.
Gray hair, then, is simply hair with less melanin, and white hair has no melanin at all. Genes control this lack of deposition of melanin, too. Exactly how hair loses its pigment remains unclear. In the early stages of graying, the melanocytes are still present but inactive. Later on they seem to decrease in number. In general, this type of graying is not associated with any disease, although it can be associated with some autoimmune processes. But graying in a young adult is not itself a sign of any health problem.
Gray hair, then, is simply hair with less melanin, and white hair has no melanin at all. Genes control this lack of deposition of melanin, too. Exactly how hair loses its pigment remains unclear. In the early stages of graying, the melanocytes are still present but inactive. Later on they seem to decrease in number. In general, this type of graying is not associated with any disease, although it can be associated with some autoimmune processes. But graying in a young adult is not itself a sign of any health problem.
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