Why Does Hair Turn Grey?

If you're hitting your late 20s, it's probable that you're starting to find tell-tale white hairs in your previously glorious, grey-free mane. The current trend for artificial grey hair amongst young, beautiful Instagram bloggers aside, all of us will turn grey at some point in our lives. Sorry; it's basically inevitable. But myths and misconceptions about the gradual whitening process abound. Can stress actually turn you grey overnight? Is shock really a contributing factor to whiteness, and is it true that science has discovered a way to send us to our graves with resplendent non-grey heads of hair? And why do people get grey hair in the first place, anyway?

Of course, the concept of the "silver fox" has done a lot to make grey hair look glam. Helen Mirren, Judi Dench, Gloria Steinem with her famous white front streaks — grey now has an edge. But it's also got sexist connotations for female attractiveness and power; while Obama has gone visibly grey while in office, it's not probable that Hillary will let her own greys shine through on the campaign trail. On men, it's a sign of venerable age, a salt-and-pepper mark of distinction; on women, it marks our "last f*ckable day," to quote Amy Schumer.

Hopefully, by the time we all hit our serious grey-maned strides in our later years, the gender perspective on grey hair will have shifted to a more equitable place. But for now, if you're looking in the mirror and freaking out, here's some science to make you feel better — and reassure you that we really are all in the same boat.

Why Does Hair Turn Grey In The First Place?

To understand what really happens to make our hair go grey and then, eventually, white, you need to get down to the heart of the matter — in this case, the follicle of the hair on your body. The production of hair in the follicle is done by epidermal cells, or keratinocytes, which "construct" hair strands. The keratinocytes also receive pigment for the hair, from cells called melanocytes. They deliver melanin to the keratinocytes — and hey presto, hair color.

It looks like greyness and whiteness are actually caused because melanocytes stop sending pigments. Hair doesn't grow continually; it goes in cycles, growing for 3-5 years, then shedding the hair, lying dormant for three months, and starting all over again. Keratinocytes continue to function through this cycle; melanocytes gradually don't. As the melanocytes gradually stop functioning — often with age — hair goes grey, then white.

How grey you go, and when, is dependent on a lot of different things. Genetics play a huge role — your DNA determines whether you have the two necessary enzymes to keep hydrogen peroxide down in the first place — but sunlight, exposure to pollutants, hormone levels, and climate are also on the list of possible causes for hydrogen peroxide build-up. Stress may also play havoc with enzyme levels and cause grey hair as a result, but we're not entirely sure.

Can Shock And Stress Really Turn Your Hair White?

The myth of hair "turning white overnight" is, as you may have suspected, largely an old wives' tale — if hair looks white in a short space of time, it's probably because stress has made all the pigmented hair fall out. But there's disagreement as to the real mechanism behind hair-whitening. In 2009, a group of scientists claimed to have isolated exactly what makes melanocytes stop sending pigment to hair — and it looks like it has a lot more to do with genetics than it does a ghostly encounter on a dark moor.

The problem, according to that study? Hydrogen peroxide. Yes, the bleach. The body produces it naturally — but in the young, hair can cope with it, because it's quickly broken down by enzymes before it can do any damage — and if it does, other enzymes work to fix it. As we get older, though, those enzymes die off, and the bleach levels rise, blocking any pigment the melanocytes send over. The result? Hair that literally bleaches itself, from the inside out.

Another theory, proposed in 2011 by a Harvard study, focussed on a signaling system between hair cells and melanocytes as the cause of greying hair. The signals, known as Wnt signalling pathways, are how the two types of cell communicate, and the Harvard team found that as the pathways broke down, hair went gradually grey. These two ideas may just be parts of a bigger whole: hydrogen peroxide breaks down Wnt signals, so it's possible that grey hair is a result of multiple signal failures.

Can Grey Hair Be Prevented?

Now that we've isolated the enzymes and cells responsible for making the grey process, surely it's just a short hop to a grey-free future. Right? Well, kind of.

A study on vitiligo, a pigmentation disorder (apparently Michael Jackson had it), found that hydrogen peroxide levels in the skin and hair could be reduced in sufferers by giving them pseudocatalase cream and then exposing them to UV light. However, the study was tiny — it only used 10 people — and the resulting media scrum about "curing grey hair" was mostly fantasy. We're a long way away from a cream that can restore color to hair overnight.

The discovery that Wnt signalling pathways are important also provides a way to stop hair going grey in the first place – theoretically, anyway. If stem cell therapy can restore the Wnt signals between your follicle and your melanocytes, you may never go grey at all. But we only discovered that in 2011; it'll take a long time before anybody starts to market gene therapy for the hair-focussed.

Interestingly, L'Oreal is apparently working on a grey-free shampoo: they've found an enzyme that's present in skin cells but not in hair, and apparently protects skin color as we age. They're hoping to produce a shampoo that somehow reproduces the same enzyme affect on our scalps.

Either way, you'd better get comfortable with your grey streaks — because science may know what's causing them, but we'll be waiting a while for a cure. Until we go grey, probably.

Images: Joey Yee/Flickr; Getty