It usually starts with one. A single silver hair catches the light in the bathroom mirror, and suddenly you're spotting them everywhere. Before long, a whole streak has joined in. Gray hair is one of the most universal signs of getting older, yet most of us have never been told what's actually going on.
Here's the short answer: gray hair isn't caused by a gray pigment. It's caused by a lack of pigment. Hair gets its color from melanin, made by cells at the root. As we age, those pigment cells stop being replaced, and new hairs grow in without color. A colorless hair looks gray or white because of the way light reflects off it.
What Happens Inside the Follicle
Your hair color comes from two kinds of melanin: a black or brown type and a yellow or red type. The mix and the amount determine your shade, with more melanin making darker hair.
The pigment is made by cells called melanocytes, which are supplied by stem cells at the base of each hair follicle. When those stem cells die off, the follicle runs out of pigment makers, and graying begins. Oddly, scientists still don't know why one follicle can lose its color more than a decade before a neighbor less than a millimeter away.
Hair grows in cycles, and pigment production is tied to them. If melanin stops late in a growth phase, a hair can turn partly gray. If it never restarts in the next cycle, the new hair comes in fully gray. That's why graying usually shows up at the roots first. There's also a curious bonus: in people who aren't balding, hair may actually grow faster once it turns gray.
Blame Your Genes, Mostly
Graying usually starts in the early to mid-twenties for men and the late twenties for women. More than 60 percent of Americans have at least some gray hair by age 40. The age when it begins seems to be driven almost entirely by genetics, and some people are even born with gray hair because they inherit the trait.
Scientists have identified several genes involved, including one called IRF4, announced in 2016 after a study of 6,000 people in Latin America. Researchers also suspect a buildup of hydrogen peroxide in the hair, combined with low levels of an enzyme that breaks it down, may play a role.
Graying even tends to follow a pattern. It usually hits nose hair first, then the hair on the head, the beard, body hair, and finally the eyebrows.
Can Stress Really Turn You Gray?
People have long said that worry gives you gray hair. There is some evidence that chronic stress can bring on graying earlier, but no definite link has been proven in people. In a 2020 study published in the journal Nature, researchers found that stress could cause hair to lose its pigment in black-furred rodents, and the color loss was permanent.
What about turning white overnight? Legend says Marie Antoinette's hair went stark white after her capture during the French Revolution, and similar stories are told about Sir Thomas More. The supposed condition even has a nickname, Marie Antoinette syndrome. But it is still called an alleged condition, and what would actually cause it hasn't been well studied.
Silver Is Normal
Gray hair arrives gradually for most people. In one survey of people aged 45 to 65, about three out of four had some gray, covering on average about a quarter of their heads. Roughly 1 in 10 people had no gray hair at all even after 60. If you notice sudden or unusual changes in your hair, talk to your doctor.
So the next time you spot a new silver strand, you'll know it isn't fading. It's simply growing in clear, and catching the light on its way out.
