From illnesses that could cause premature graying to the science behind aging hair, here’s what you need to know.

Whether you discovered your first silver strand or you’ve decided to let your natural hair color shine, it’s normal to find yourself wondering, why does hair turn gray? And while we’ve touted ways to embrace and style your gray hair, the science behind why white and gray strands occur is actually quite interesting.

We’ve all heard the thought that stress causes gray hair, and in fact, recent studies suggest a link between the two. But, there are so many more reasons why your locks might be getting lighter. In fact, general aging and even your genes could have a lot more to do with your silver strands than you might think. And underlying health conditions like vitamin deficiency or alopecia could even be a factor.

Ahead, we asked dermatologists to explain why hair turns gray, what causes premature graying, and if it’s possible to reverse gray hair.

“Gray hair is really hair with less melanin, what gives skin and hair color,” explains Azadeh Shirazi, M.D., a board-certified dermatologist. “While white hair completely lacks [melanin]. With aging, there’s a gradual decline in the number of stem cells that mature to become melanin-producing cells. These cells may wear out, become damaged, or lose the support systems meant to keep them working.”

Apparently, our genes are also a factor. “​​Over time as we age, our cells do not produce as much melanin resulting in gray hair (decreased melanin) or white hair (absence of melanin),” explains Janiene Luke, M.D., a board-certified dermatologist at Loma Linda University’s Faculty Medical Group in California. “There is a genetic component and this can be seen in those who exhibit premature graying (that occurs earlier in life when one is in their 20s or 30s). However, hair growth and hair pigmentation are highly regulated processes with multiple genes and cell signaling molecules involved, where any disruption of these processes can lead to gray hair.”

What’s on our scalp, or rather, hair bulb, also plays a part, according to Marisa Garshick, M.D., F.A.A.D., a board-certified dermatologist. “As we age there is a buildup of hydrogen peroxide in the hair bulb which can destroy the pigment-producing cells, leading to decreased melanin and gray hair.”

So basically, as we age our cells produce less melanin, which leads to gray hair. But, if you go gray much earlier than anticipated (say, at age 20 instead of in your late 30s or 40s), there might be something more at play.

Premature graying is thought to be genetic, according to Dr. Garshick, and “may even be related to a specific gene known as interferon regulatory factor 4 (IRF 4) which may help to regulate melanin production.” But there are a number of health conditions that could lead you to go gray, too.

According to all of the experts we spoke with, the following causes gray hair:

Unfortunately, there is not much to do to stop graying when it is part of the normal aging process, explains Dr. Luke. “Early on in the process, however, if there are reversible causes leading to graying (i.e. smoking, nutritional deficiencies), people can try to make lifestyle modifications such as quitting smoking and maintaining a healthy diet packed with nutrients and antioxidants to help protect the cells involved in hair pigmentation.”

But, Dr. Shirazi thinks that the future might hold some options. “Possibly in the future as new studies show by stimulating stem cells back into action, pigment-producing cells can be revitalized to reverse gray hairs.”

Emily Goldman is the senior editor at Prevention. She’s spent the last few years editing and writing health, wellness, beauty, food, and more for Marthastewart.com and Bridalguide.com. She’s loved all-things health and wellness since starting her bi-weekly podcast Pancreas Pals—a series all about the highs and lows of living life with Type 1 diabetes. When not podcasting, she spends most of her time curled up with a good book or watching a period piece on BBC. 

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