It’s easy to see why going grey is considered a sign of a stressful life – just look at pictures of prime ministers and presidents before and after their time in office.
It’s also one of the most visible signs of our advancing years; around 90 per cent of us will be grey by the time we’re 60.
Unsurprisingly, the industry related to preventing or covering up this loss of hair colour is estimated to be worth tens of billions of dollars globally a year, and the wild west that is social media has supercharged the number of people claiming their products can prevent or reverse early greying.
But to biologists, grey hair is not just a cosmetic issue. Greying hair provides a uniquely easy way to watch and study how our bodies age.
The recent discovery that the process can sometimes go in reverse, and strange cases of grey-haired people regaining their hair colour while on certain medicines, offer not just the realistic hope that hair can be restored to its former glory…
They also herald the exciting possibility that we could use similar techniques to reverse ageing in other tissues of the body.
The science of greying
Hair turns grey when special cells at the very base of the hair, known as melanocytes, stop producing the pigments that normally give opaque colour to the growing hair, such as eumelanin (brown-black) or pheomelanin (yellow-red), or when there are too few melanocytes to effectively add colour to the hair.
In healthy, pigmented hair, a population of cells known as melanocyte stem cells sit in a ‘bulge’ to the side of the hair follicle.
Each time a new hair starts growing, these stem cells travel to the base of the hair to mature into new melanocytes – so age-related deterioration of these stem cells reduces the number of healthy melanocytes producing pigment in the hair.
Eventually, when there are no melanocytes or pigment left at all, hair grows as a virtually translucent strand of keratin, making a person’s locks appear white.
The gradual loss of melanocytes and melanocyte stem cells seems to be a natural part of the ageing of the hair and scalp system. Why these cells fail earlier than the ones that produce the hair itself is not known.
What is clear is that periods of intense stress – and even other environmental factors, such as exposure to pollution or radioactivity – can also trigger problems in these cells that lead to early greying.
Our genetic ancestry also makes a difference to how soon and how intensely we’ll go grey.
Those of European descent are most likely to go completely grey first, with French Europeans particularly prone, while those of sub-Saharan African ancestry have the lowest frequency and intensity of greying in the world.
Going very grey before the age of 30 is considered ‘premature greying’ and is most often a sign of a deficiency in a key vitamin or mineral, particularly a lack of B-vitamins, or low calcium or iron, although it can also be a symptom of rare genetic disorders.
Our understanding of the complex relationship between age, stress, stem cells and pigment production is advancing fast.
We now know that the pigment-producing melanocytes can start to fail due to oxidative stress – a constant type of chemical damage that accumulates with age.
Our melanocyte stem cells can also suffer a range of fates, which can cause greying. With age, they may start to die before turning into melanocytes, or they may fail to mature into melanocytes properly, getting ‘stuck’ in a limbo-like state that is neither one thing nor the other.
In cases of severe stress, they can all turn into melanocytes at once, depleting the pool of stem cells needed to pigment new hairs in the future.
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Focusing on follicles
Dr Melissa Harris, a biologist at the University of Alabama at Birmingham, in the US, is one of the world’s leading experts in grey hair.
Studying mice, some of whom are genetically altered to go grey early, allows her to explore how stem cells age in an easy-to-see, non-invasive way.
“The pigmentation process tells us a lot about the origin of certain cells, how they move, and why they start to fail,” says Harris.
“The melanocyte stem cells are a stem cell population that mimics a lot of other adult stem cell populations, too, in that they are dormant for a time, then they kick in and start turning into other important cells.”
The neat thing about studying hair, says Harris, is that she can activate this stem cell population simply by plucking a hair. This kick-starts the dormant stem cells to mature into a new population of melanocytes.
A better understanding of the way these stem cells function and falter could help unlock new methods to treat a range of age-related health problems, such as age-related muscle loss (a major cause of injuries), loss of mobility and frailty in older people.
“As scientists, we’re always looking at ways to answer questions in the most straightforward and ethical fashion.
“Studying grey hair can help tell us things that are applicable to the stem cells that turn into, say muscle tissue, which also show a decline with age but are really, really difficult to study.”
Dr Martin Picard, an associate professor at Columbia University, New York, is interested in why the hairs on our head or face go grey at different times.
He believes this could help us understand the broader question of why cells in the body deteriorate or age at different rates to others, why some individual cells are more resilient to stress, or even why some people die earlier than others.
“I have hairs on my head that have been grey for about 10 years, and the one next to it is dark.
“Each hair is a mini-twin of the other. It’s just a beautiful model to study how, in a highly controlled environment – same body, same genetics – you can get an entirely different outcome.”
Strands of evidence
Fascinatingly, after inviting people to send him their grey hairs in 2020, Picard found some people had hairs with colour in the tip – the oldest part – that then went grey or white in the middle, and then had started growing with colour again near the root.
These banded specimens were proof that hairs that had lost their pigment, for weeks or even months, could spontaneously regain it.
“We got this hair that was dark at the root, and then a beautiful, completely white segment for two centimetres, and then dark again at the tip.
“When we interviewed the woman who sent it, the time points matched up perfectly with the most stressful two months of her life, when she’d broken up with her partner, had other family issues, and was looking for a job and a place to live.
“The return of the colour tracked with when she had reconnected with her partner, found a job, and said life was good again.”
Picard’s work not only showed that a single hair can act as a physical record of our stress levels, but also that the body can reverse loss of pigmentation under the right conditions.
“There’s likely a kind of energetic process that drives the greying process,” he says. “Sometimes energy has to be prioritised for other things and sometimes it is available again for making pigment.
“This challenges, I think, the traditional perspective that ageing is just an accumulation of molecular damage; that it’s progressive, it’s linear, and it’s irreversible.”
The special striped hairs at the heart of his work are not as rare as you might think. “Once you start looking, it’s pretty common,” says Picard.
“I’ve had two or three hundred people send me pictures of hairs like this they’ve found now. I’ve even found a few on my own head.”
What can be done about grey hair?
More and more drugs are being found to have remarkable, time-reversing effects on grey hair, too.
A recent review of medical literature by scientists based in Xuzhou, China, found that trials of at least 17 different drugs had reported re-pigmentation of grey hair as a side-effect. These ranged from antibody-based cancer therapies to anti-inflammatory drugs for psoriasis.
One particular type of immunotherapy, known as anti-PD-1/anti-PD-L1, caused drastic reversal of grey and white hair in 14 patients being treated for lung cancer.
Even therapies for hormone disorders, Parkinson’s disease and Alzheimer’s disease have caused hair re-pigmentation, albeit very rarely.
It all leads to the question many readers will want answered: what can be done about my grey hair?
If certain drugs can reverse the greying process, and the body itself can restore hair colour after losing it for a while, is a genuine treatment for grey hair around the corner?
Well for a start, many of the drugs described above are seriously heavyweight therapeutics, with a range of complex effects on the body.
It’s unlikely any of these would ever be directly applied to a largely cosmetic problem like grey hair without extensive modification and much more research on how they cause the effects that they do.
What’s more, these drugs don’t seem to have caused re-pigmentation in all the grey-haired people who took them, suggesting the effects might be limited to certain ‘types’ of greying only.
There have also been reports that some plant extracts used in traditional or indigenous medicine, such as those of American herb Eriodictyon angustifolium or the Chinese plant Polygonum multiflorum can slow greying, and re-pigmentation has even been observed in response to injuries to the scalp during skin cancer surgery.
In 2025, a study by scientists at Nagoya University in Japan showed that luteolin, a naturally occurring antioxidant found in vegetables such as celery, broccoli, carrots, onions, and peppers, had completely reversed greying in mice.
Other research is focusing on a suite of compounds that appear to boost the pigment-producing abilities of melanocytes in vitro – in other words, in a test tube rather than in the body of a living organism.
These include peptides that mimic hormones that boost pigment production, and antioxidants that help prevent the breakdown of melanocytes or the pigments themselves.
Other approaches focus on drugs that block the body’s stress response, similar to so-called beta blockers, although again these would likely have unwanted whole-body effects in their current form.
Despite these significant caveats, Harris (who is not directly working on treatment for grey hairs) believes an important breakthrough is not far away.
“We have tools now that I think are getting us closer to it,” she says. “There’s case after case in the literature that shows it’s possible. We wouldn’t be having this conversation if it was all totally answered, but I think it’s getting closer.”
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A colourful future
One of the key questions that remains is whether all people with grey hair still have some residual melanocyte stem cells that can be reawakened, or whether grey hair reversal is only possible in certain types of greying (like when the stem cell population is healthy but the melanocytes are failing).
Harris believes that, ultimately, a truly permanent ‘cure’ for greyness must target the root of the pigmentation process: the melanocyte stem cells.
“Many approaches are looking at boosting melanocytes, but my view is that those methods are limited, because as soon as you lose all your melanocytes, you can no longer boost them.”
Harris hopes that all this research will lead to a wider understanding of the ageing process.
Harris has, for example, seen tantalising evidence that older people on anti-PD-1/anti-PD-L1 therapy, the immunotherapy treatment that caused drastic reversal of greying in grey and white-haired people, saw benefits to muscle mass. This might suggest the drug has a broader anti-ageing effect on other stem cells in the body.
“That could be the first bit of evidence that we’re on the right track,” she says.
While next generation anti-ageing therapies are the long-term goal, in the day-to-day Harris continues to raise awareness about greying and advises the regular stream of people contacting her about their unwelcome greys.
“People may think that it’s a silly topic or about straight-up vanity. But I get emails a lot from people who feel like their physical appearance affects their quality of life, or that their outward appearance doesn’t reflect their inner self. It’s important to them.”
Busting myths about greys
Is stress causing my grey hair?
Almost all of us will experience a certain amount of greying as we age, but greying can be accelerated by severe or chronic stress.
That said, aside from drastic cases, where high stress causes a person to go grey fairly quickly, it is often difficult to say whether grey hairs are appearing because of age, stress, or a combination of both.
Does plucking grey hairs make more grow back?
No. Plucking a hair simply resets the hair cycle, and a single new hair will grow in its place. Plucking a hair does not seem to affect other follicles nearby.
Do grey hairs grow faster?
Many people feel like their grey hairs seem to burst out of their head and are particularly unruly.
There may be some truth to that: the diameter of a non-pigmented hair can be up to 17 per cent greater than pigmented hair, and they can grow a little faster – around 8 per cent according to some research.
Can hair turn grey or white overnight?
Although there are several famous cases of people’s hair turning white overnight – such as Marie Antoinette or Sir Thomas More, both just before they were beheaded – these accounts seem likely to be exaggerated.
Hair can only turn grey or white as quickly as it comes out from the follicle, which in humans is around a centimetre (0.4 inches) a month. Plus, not all the hairs on your head are in a growth phase at any one time, meaning they can’t all go grey at once.
There’s no known way for hair that has already grown out of the scalp with pigment in it to suddenly be stripped of its colour, other than bleaching it out with chemicals.
What’s more likely is that these famous historical figures went grey gradually while on the run, on trial, or imprisoned, and their change of hair colour was suddenly revealed to the world when they emerged to be publicly executed.
Will dyeing my grey hairs make me go grey faster?
Most dyes form a simple layer over the outer part of the hair and don’t affect the pigment underneath. However, harsher chemicals like bleaches can damage the hair follicle more seriously over time, causing hair loss and loss of pigmentation.
Can I stop my hair going grey?
The big question! A healthy diet and supplements can prevent very premature greying associated with vitamin deficiencies.
Avoiding stressful life situations, and other lifestyle choices such as smoking, could in theory help prevent the cellular stress that accelerates greying.
There are also many compounds and plant extracts that have shown some promise in preventing greying or are being studied for their ability to restore colour to grey hair.
But there are currently no clinically proven or reliable treatments to stop the natural greying of our hair as we age.
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