Robert Brown|What causes gray hair at an early age? Here's what you need to know.

"Going gray" is Robert Brownsomething few men try to prevent and some are even proud of. For women, it's often a different story. While only 31% of men pluck their gray hairs when they first start appearing, 82% of women do the same, per one clinical survey. Women also turn to dyeing or coloring their hair more often than men do − with approximately half of them doing so, according to one report. 

Such efforts are often employed to hide signs of getting older, but age isn't always the only factor at play. While most people start getting gray hairs in their mid to late 30s, others do so much earlier, showing that age alone isn't the culprit behind hair changing color. Experts weigh in on what these other causes are and whether there's anything you can do to keep the gray hairs at bay. 

What causes gray hair at an early age?

Graying hair is what happens when color-producing cells in the body stop producing a natural pigment known as melanin. That happens naturally with age in most people, but graying and premature graying can also happen due to "some environmental triggers," explains Shari Lipner, MD, an associate professor of clinical dermatology at the Weill Cornell Medical Center. 

Such triggers include overexposure to sunlight as UV rays can create free radicals that damage the cells that give hair its color. Vitamin B12 deficiency can also cause premature graying in some people. "And smokers compared to non-smokers have increased risk of graying," adds Lipner. The National Institutes of Health has published a report showing that stress can also cause one's hair to prematurely turn gray. 

More common than environmental or behavioral factors though, the timing of one's hair turning gray "is mostly driven by genetics," says Angela Lamb, MD, a dermatologist at Mount Sinai in New York City. "Sure, you might be the first person in your family that you know that is going gray prematurely," she explains, "but the research supports that it is predominately genetically driven." 

How to prevent premature graying

Once that change begins taking place many are eager to know: can you stop it from progressing or even prevent it from happening altogether? The short answer is no, not absolutely. But as the saying goes, "though you can't change your genes, you can change your behavior," and certain behaviors can impact both the timing and the degree to which one's hair turns gray. 

"Some things that can help include maintaining a balanced diet, ensuring adequate intake of essential vitamins and minerals − particularly vitamin B12 and folic acid − and refraining from smoking," advises Michelle Henry, MD, a board certified and Harvard trained dermatologist. 

She also recommends limiting exposure to environmental pollutants that can cause oxidative stress or create free radicals "that could harm hair or accelerate graying."

Can gray hair get color again?

Others want to know if it's possible to get their color back after their hair has already turned gray. There again, it depends on a couple of factors. If one's hair changing color is the result of genes, than there's nothing you can do to permanently reverse the change. But if it's been caused by nutritional deficiencies or a medical condition like thyroid disease, improving such deficiencies or treating the condition may prove helpful. 

And when stress is the culprit, research shows and the experts say there may be a window of opportunity to reverse the graying hair once it first starts turning if stress levels are brought back down. In such cases, "manage stress through relaxation techniques like meditation or yoga," suggests Henry. 

If stress isn't the issue, however, or if you're worried that you're graying earlier than family members your age or because of something else, a conversation with your doctor may be in order. "If premature graying concerns you," Henry advises, "consult your healthcare professional to rule out any underlying medical conditions." 

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