Science

Inside the Follicle: What Actually Slows Down When Hair Goes Grey

Every strand of pigmented hair you grow is the work of a small team of cells called melanocytes, nestled inside the bulb of each follicle. They produce melanin — the same pigment that colours your skin — and inject it into the keratin as the hair shaft is built. When melanocytes slow down or die off, the strand grows without pigment. That's grey.

It's a stem cell story

Melanocytes don't live forever. They're replenished by a reserve population of melanocyte stem cells living in the upper part of the follicle. With each hair cycle, those stem cells migrate down to the bulb, mature into pigment producers, and eventually die. The reserve depletes over time.

The current dominant theory, supported by a 2023 study from NYU's Grossman School of Medicine, is that melanocyte stem cells get stuck. They lose the ability to move between the niches that signal "mature" versus "stay in reserve" — and stuck stem cells stop differentiating into pigment-producing cells. The hair that grows from those follicles is white.

Genetics sets the timing

The single biggest predictor of when you'll go grey is when your parents did. A large 2016 study identified IRF4 as the first gene specifically linked to grey hair — it's involved in regulating melanin production. Several other genes are likely contributors, and the timing is overwhelmingly heritable.

Stress probably plays a role — but a smaller one than people think

A 2020 Harvard study showed that acute stress can drive melanocyte stem cells out of the niche prematurely, accelerating greying in mice (and likely humans). Reverse the stress quickly enough, and some pigment can return. But chronic background stress is not the main driver. Genetics is.

What this means in practice

There is, as of now, no proven treatment that reverses or prevents greying in humans. Several promising candidates are in early research — mostly aimed at coaxing stuck stem cells back into circulation — but nothing has cleared a clinical trial. If you see an ad promising otherwise, the ad is lying.

The most honest thing we can say: greying is a normal, heritable, and largely unstoppable process. The more interesting question isn't how to stop it — it's what we collectively decide it means.

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The Science Behind Why Hair Goes Grey

Hair colour comes from melanocytes, the cells in our follicles that produce pigment. As we age, these cells gradually slow down — and eventually stop — producing the melanin that gives hair its colour. Genetics set most of the timing. If your parents went grey early, you probably will too. But emerging