This is a lot simpler than people make it.  Gray hair is a happenstance of life.  At the end of the day, genetic, racial and chemical considerations determine when you go gray.  Let’s briefly look at each and dispel a myth or two along the way.
Chemical: Your hair consists of two parts, a shaft (the visible part above the skin line) and the root (the portion located below the surface). The root contains hair follicles, which contain color-producing cells called melanin (yes, the same melanin that contributes to skin color). Any disruption in melanin production or damage to the hair follicles, such as folliculitis and especially the normal effects of aging, can cause graying. This graying may be physiologic and timely, or it can be premature. An additional consideration to graying can be the physiologic build up of hydrogen peroxide. This naturally occurring chemical actually bleaches the hair.
Racial: Bet you didn’t know that on average, different racial and ethnic groups go gray at different rates. Whites start graying in their mid-30s. Asians begin graying in their late 30s. African-Americans seem to begin graying in their mid to late 40s. Most people will have noticeable and significant graying by age 50.

Genetic: Simply put, graying is predetermined based on your genetic composition. You should already have a good idea if and when you’re going gray by looking at your parents and grandparents.

Doesn’t stress make you gray?  Isn’t that why Presidents go gray while in office?

• Presidents go gray in office because they’re at the age when people go gray while in office.
• The stress you’re thinking of (‘freaking out’) isn’t the same as physiologic stress, which is a disruption of the body’s normal functions. Such biological stresses can cause disruption of any bodily function. This is why so much confusion exists around ‘stress’. When scientists or your physicians are describing the effects of stress, it’s much deeper than your anxiety attack, which isn’t going to turn you gray overnight.

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