The Science of Gray Hair

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The Science of Gray Hair

Seniors' Health
The Science of Gray Hair
The Science of Gray Hair
Gray hair can be a signature life event. Find out why it happens.
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Reviewed by the Faculty of Harvard Medical School

The Science of Gray Hair
Gray hair. To some, it's the beginning of the end. Others accept it as a public token of wisdom. A few think gray hair is caused by stress and worry, though there is no evidence to support this concept.
Whether dyed, rinsed or allowed to grow naturally in its spongy, wiry manner, the arrival of gray hair can be a signature event.
Health, heredity and environmental factors all affect when your hair begins turning gray. But the main cause is aging.
Getting to the root of it
It all begins when your body stops producing melanin. Each strand of your hair grows out of a follicle that has cells filled with melanin. These melanin-filled cells are called melanocytes.
Melanocytes pass melanin to adjoining cells called keratinocytes. These produce keratin -- hair's chief component. When keratinocytes undergo their scheduled death, they retain melanin. The pigment visible in hair and in the skin lies in these dead keratinocyte bodies.
Over time, the amount of melanin in the keratinocytes decreases. Gray hair is simply hair with declining levels of melanin. White hair has no melanin at all.
The declining presence of melanin also appears to contribute to the lack of moisture in gray or white hair. So as your hair becomes lighter in color, its texture becomes dryer and coarser. That’s why gray hair tends to be more curly or wiry.
The process of turning gray
At the beginning of the graying process, follicles produce colorless strands in a random pattern. For unknown reasons, the first gray or white strands usually appear on your temples and the top of your head.
Your hair doesn't actually "turn" gray -- it grows in this way. Every day, hairs fall out and new ones replace them. At any given time, about 85% to 90% of your hairs are actively growing, while the rest are in a resting state.
Typically, 1 strand grows for 2 to 4 years. It then naturally enters a resting state for about 2 to 4 months, after which it falls out and is replaced by a new hair. On average, most people lose about 50 to 100 strands of head hair a day.
Darker hairs are older and fall out sooner than the newer gray hairs. So, when it seems like you "went gray overnight," in reality the gray strands just became more noticeable in the normal course of shedding. This is especially dramatic for people with telogen effluvium, a temporary condition in which a major stress, such as severe illness, surgery or sudden weight loss, speeds up shedding to 300 hairs a day.
When it happens
There is currently no scientific way to tell when a particular cell or group of cells will stop producing melanin. In the early stages of graying, the melanocytes are still present but inactive. Later on, they seem to decrease in number.
This natural process of graying can begin as early as your teens. In most people, however, graying first becomes noticeable in their late 30s.
Some researchers have shown that gender plays a role in graying. The average male starts to gray around age 30, while women typically began to notice lighter strands around age 35.
Genetics are also a contributing factor. In some families, many members develop white hair in their 20s.
But this biological fact of life varies greatly from person to person, which lead dermatologists and geneticists to conclude that age is not the most accurate indicator of when gray hair will appear.
Some potential reasons
Medical experts have been able to find a relationship between graying and the environment and graying and lifestyle choices.
They have also shown a relationship, to some degree, between graying and illnesses and conditions.
  • Smoking. Smokers are more likely to go gray at a young age.
  • Illnesses. Sometimes, the arrival of gray hair can be a sign of an underlying health problem. Werner's syndrome, a disease that mirrors the symptoms of aging in people as young as 20, can spur the premature growth of gray hair. Pernicious anemia, a disease marked by a vitamin B12 deficiency, is sometimes associated with decreased melanin production. Any illness or condition that causes your hair to fall out may reveal graying strands formerly hidden by your original hair color or sheen. For example, slow-growing or new gray wisps may become more obvious if you are coping with alopecia areata, an autoimmune disease that causes hair to fall out in small patches. Other examples include thyroid disease and vitiligo, a condition of unknown cause in which melanocytes are lost or destroyed, perhaps because the immune system "misfires" and attacks normal skin. If the scalp is involved, areas of white hair may develop.
  • Drug treatment and alternative medicine. Several drugs can cause growing hair to stop its growth cycle and fall out. For example, drugs such as lithium (used to treat manic depression) and methotrexate (used to treat some forms of arthritis and cancer) can contribute to hair loss, revealing more gray strands. Interestingly, some cancer patients, whose gray hair falls out as a result of chemotherapy, experience regrowth of the lost strands in their original color. This phenomenon suggests that melanocytes that are producing less melanin can be stimulated to make more, although how this occurs remains a mystery.
Embrace your individuality
English humorist and author P.G Wodehouse concluded that the guillotine is the only cure for gray hair. Religious texts, on the other hand, consider the loss of pigmentation as "the beauty of the aged." At the very least, the first sign of white specks can be taken as affirmation that you are aging normally.
Many products promise to return your hair to its natural color. Credible scientific evidence of such claims has not been verified. At best, such products are temporary. And some may cause harm, depending on the chemicals they include. For now, people with gray hair have two choices: leave it gray or dye it. Either way, you’ll have plenty of company.

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Last updated September 02, 2014

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