FactSentinel

Hair turns white because the cells that produce pigment stop doing so, not because the hair strand itself changes color. Each hair follicle contains melanocytes, specialized cells that make melanin and transfer it into the growing hair shaft. Melanin gives hair its brown, black, red, or blond shades. With age, the melanocyte stem cells in the follicle gradually decline or become depleted, so new hair grows in with little or no pigment. Hair that appears white or gray is therefore mostly unpigmented hair, and the strand itself contains no true white pigment.

The evidence is well established in dermatology and stem cell research. Studies of human and mouse follicles show that graying coincides with a loss of melanocyte stem cells and reduced melanin production. Hair is also made of keratin, which is naturally translucent, so without melanin, light scatters through the strand and makes it look white or silvery. Gray hair is typically a mixture of pigmented and unpigmented strands, which creates the optical effect of gray.

A common misconception is that hair already grown can turn white overnight from shock or stress. Because the visible shaft is made of dead keratin, it cannot change color after it has formed. Stress may affect pigment-producing cells in the follicle and influence hair that grows afterward, and research supports that link, but it does not bleach existing hair. Another myth is that plucking a gray hair causes more to grow in. It does not.