It happens to all of us: at some point or another, we spy that first dreaded grey hair, and the onset of old age begins. In my case, at the ripe age of 25.
But why our hair turns grey as we age has not been well understood, until now. US scientists believe they may have uncovered the reason behind the greying process, revealing that our pigment-making cells - melanocytes - lose the ability to mature over time. Melanocytes are the cells in each hair follicle that produce and contain the pigment melanin, giving hair its natural colour or shade.
As reported by the BBC, the Langone Health team from New York University (NYU) studied the process in mice, which possess identical cells for the colour of their fur.
Just like how we shed and grow hair, melanocytes - which also reside in the hair follicles - continuously decay and renew. New melanocytes initially begin as stem cells, which mature and develop into the pigment-producing cells over time.
However, these fledgling melanocytes get lazy, the researchers noted, increasingly so as the hair repeatedly ages, sheds and regrows throughout a person's lifespan. Eventually, these sluggish, immature cells give up roaming around the follicle, which causes them to become fixed in place. As a result, they get "stuck" in limbo and fail to mature into fully-fledged melanocytes. With no pigment being produced, the hair turns grey, white or silver.
According to the British Association of Dermatologists (BAD), ongoing work on melanocytes might aid the understanding and treatment of certain cancers and other medical conditions, such as alopecia and vitiligo.
The research may also provide a foundation for future work into possibly reversing or preventing the greying process, the scientists noted.
"Our study adds to our basic understanding of how melanocyte stem cells work to colour hair," study lead investigator Dr Qi Sun, a postdoctoral fellow at NYU Langone Health, told the journal Nature.
"The newfound mechanisms raise the possibility that the same fixed-positioning of melanocyte stem cells may exist in humans. If so, it presents a potential pathway for reversing or preventing the greying."
Other research has floated the idea that poor nutrition is a possible, but treatable cause of premature greying, while some scientists claim stress can play a role in the hair turning white, suggesting that combating anxiety might help to temporarily restore pigmentation.
Other studies have proposed that genetics, or our DNA, partly determines when our hair begins to grey.
While it's tempting to pluck out any stray or rogue grey hairs, experts advise against it - just like popping a pimple, the short-term satisfaction isn't worth the long-term damage. Removing the strand won't stop the next one that grows from the same follicle also being grey, and if you damage the follicle, it may impact the growth of new hair - meaning over time, you could be left with bald patches.
"The obvious implication of this research, when it comes to the general public, is that it means being one step closer to finding a way to reverse our grey hairs," Dr Leila Asfour, from the British Association of Dermatologists, told the BBC.
"But this study's results help the medical field better understand other conditions where these stem cells may have a role - for example, understand the underlying nature of the deadliest skin cancer we treat called melanoma."
Dr Yusur Al-Nuaimi, from the British Hair and Nail Society, added: "We are already discovering more about the potential of stem cell therapies for conditions including hair loss and studies such as this one, with new findings about the colour-producing cells, may lead to an array of future treatment options for our patients."
