Several times over the past few years, I have noticed something strange in my hair pigmentation: a strand of hair that appears to be going gray from the tip, upwards. Or conversely, had started to go gray and then changed its mind. When the phenomenon was mentioned online, the majority of people commented that such a thing could not scientifically occur, while a very small handful of people divulged that they had had the same experience. Thus began a quest to understand how this and other aspects of going gray really occur, and it led to Prof. Des Tobin, Professor of Cell Biology and Director for Skin Sciences at the University of Bradford in the north of England. Prof. Tobin granted an insightful interview that not only answered the initial question, but also revealed a glimpse of just how much there is to know about this skin appendage we call hair and how pigmentation really works.
When a human is in its mother’s womb, it first develops the skin, also known as the epidermis – the outer layer of skin. Out of the epidermis grows the follicle, which is why hair is determined to be an appendage of the skin, the same way a nail is; these are some of the products of the skin during development.
Pigment cells, so-called melanocytes, are derived from the same part of the embryo as neurons are, from what is called the neural crest. One could view pigment cells in the skin as sorts of clusters of neurons, and scientists well know that neurons are extremely sensitive to stress, particularly what is called oxidative stress – a type of free-radical damage humans get from aging, pollution or psycho-social stress.
Melanin, hair colour and aging
There are several genes that control hair colour (and skin colour). For instance, the Melanocortin 1 Receptor Gene (MC1R), where the ancestral type produces dark brown/black pigmentation, but variations in this gene lead to more red/yellow pigment (e.g., Celtic). There are also genes for blondeness eg. ckit ligand gene, tyrosinase-related protein-1 gene etc.
Hair colour does not determine at what age melanin cuts off and loss of pigmentation occurs. However, different ethnicities normally gray at different rates. Caucasians gray the earliest, followed by Africans, followed by Asians.
Gray hair still contains some pigmentation, whereas white has none at all.
Why have pigmentation at all?
In terms of pigmentation of the skin, it is very clear it exists in relation to sun protection from damaging UVA and UVB rays. The situation with hair is less clear, although there is some suggestion that having melanin in hair, the actual molecule called melanin, is an important – or was an important – detoxifying system in early evolution. Melanin is a very ancient molecule; it exists in the black gills on mushrooms when you turn them over, also pretty much in all other animals in the animal kingdom, even fish and birds and insects. The reason why it is there is because it binds toxins, metals and chemicals in a safe way so it can move them away from living tissue. There is some evidence that humans evolved along seashores and riverbanks, where their diets were very fish-rich, which of course poses the risk of ingesting heavy metals. In certain situations, if one’s diet is very high in fish, there is a potential for heavy metal poisoning, and there is some evidence that melanin can bind these heavy metals and make sure they do not get into the living cells.
Humans are unusual in that they have such luxurious, pigmented scalp hair. Most of our primate cousins, like chimpanzees or gorillas, have useless head hair by comparison. There is something about the human evolutionary switch that made a connection with very long and luxurious face and head hair, including beards as well as scalp hair. This has led leading scientists to believe there could be a connection within the pigment system because melanin is such a good “mopper-upper” of potential toxins.
Hair and the Growth Cycle
Hair grows at approximately 1 cm/month. Most normal hair cycles are approximately 3-7 years long, after which the hair grows out and a new one replaces it from the follicle. This wide-ranging cycle explains why some people, even if they do not ever cut their hair, can only ever grow it to their shoulders, whereas other people who do not ever cut their hair can grow it down to the floor.
In some rare cases, because their genetics allow that continuous growth to be expanded, there are some huge quotas in some individuals. For instance, there is a particularly famous Chinese woman whose hair has been growing continuously for about 35 years. Her hair is maybe 3 metres long, which is an huge amount of hair. She has never cut it; she keeps it in a braid or turban.
So when your hair stylist tells you that split ends will stunt growth: they are wrong.
The Effects of Stress on the Hair
There is a strong and proven brain-skin axis (PDF). Scientists know that psoriasis and eczema on some people flare under stress, and in thinking in terms of the brain-skin connection in context of overall skin function, the effects of stress on hair growth and pigmentation are similarly observed.
In the context of stress and bereavement, and shocks like that, there is good evidence now that there is a link between hair or pigmentation loss and psycho-social stress. In the past it had never appeared like you could connect the situations – did the hair go gray/fall out because the person was stressed, or was the person stressed because their hair went gray/fell out? But there is good evidence now in animal models, particularly in mouse models, where it has been shown that if they are, for example, exposed to sonic stress (the sort of stress people use to keep moles out of their garden, a kind of sound-deterrent), it irritates the mice significantly to the point that they can actually shed their hair.
Stress is a kind of assault on the hair follicle. Under clear assault, the hair is shed under its normal state and then grows back again in the recovery state. Sometimes you get a partial effect instead of the actual shedding, resulting in going gray, due to the pigment cells being very, very susceptible to stress.
In some people, if they get a shock or some other bereavement or something else, and they have straight hair, you can sometimes see that there has been a shock line across the full array of hair that reflects a period of time when they have had that shock. Similarly, if someone went on a crash diet, or had some other major change to their physiology, you can sometimes see the pigmentation loss in a line across tens of thousands of strands of hair, not just one.
Can Hair Really Be Scared White?
We have all heard stories about people whose hair has gone white following a giant fright. Some historical notables would be Marie Antoinette before the guillotine, and Thomas More before he was hanged. Or the 1918 incident of The Old Scow at Niagara Falls, the story of the rusted boat stuck at the top of the Canadian falls and James Harris, the crewman who was so stressed out that his hair turned white overnight.
This phenomenon comes from an attack of what is called alopecia areata, which is an autoimmune disease that can be triggered by stress, whereby the pigmented hairs are preferentially targeted, and the white hairs are spared. As one ages, most individuals have a mixture of dark and gray/white hair, a mix by which it still looks very dark from a metre away. If such a person has a preferential targeting of the pigmented hairs, and those hairs are shed in three days to a week, they will then suddenly and shockingly unmask all the white hairs en masse, giving the impression of “going white overnight.”
A human needs to lose approximately 1/3 of their hair density before it would actually appear to be thinning from a healthy head of hair, so the sudden white hair can therefore appear to be just as dense as the hair that was there before, when the person has in fact just lost their pigmented hair.
Going Gray in Reverse
Back to the question that inspired this article: How does one’s hair go gray from the tip to the root? It turns out one of the initial suppositions was on the right track.
While hair is growing it is in a phase of the growth cycle that produces active pigment. You have probably noticed your hair grows and falls out, grows and falls out, in a natural cycle that likely lies within the 3-7 years mentioned above. The pigmentation contribution to the hair fibre can only occur when the follicle is actively producing hair, so when it goes to the other phase of the cycle, like the resting phase, or what is called the regression phase, there is no active pigment transfer into the hair. The early stages of going gray can be likened to a car running out of fuel; it stutters along until it stops entirely.
It is therefore not unusual for men, with their beards or chest hair, or men and women if they do not dye their scalp hair, to notice that the tip of the hair is white, that the part that is the oldest part of the hair is white, and what is called the proximal part, the part toward the skin and into the skin, is dark. This occurs when the follicle has already experienced a kind of aging insult, and has in a sense had its pigmentary apparatus wobbled or shaken to the point that for a few weeks or months it ceases to produce pigment. But then it recovers again, allowing the follicle to continue producing pigmented hair. Normally when that particular hair falls out and the next hair grows into the same follicle, it will actually grow out white this time.
In these instances, the two or three toned loss and gain of pigmentation on one hair fibre would not have a sharp demarcation line as might be the case with stress-related pigmentation interruption, but would be more of a gradient. It’s not like a light being turned off and on again, but more like a lamp on a dimmer switch being slowly turned down and turned up in the same cycle.
Hair cannot tell a lie
Hair is a very clear window into what a person’s body has experienced. Archaeologists, for example, and even forensic scientists, can tell a lot about what has happened to the person in the 2-5 years prior to their death, if they find complete hair strands. Because the hair grows at approximately 1 cm/month, what the body was doing during that time, and the time involved, is locked in. So, if you find a foot-long strand of hair, and you know the tip end and you know the root end, then you can investigate that for evidence of nutrition, and of exposure to toxins and pollutions, because they will be locked in there.
The good thing about that is that you can time it to within a calendar month or even less. Therefore, if someone lies and says they did not touch a certain drug, but you know the rate that their hair grows, and you know the length of it from its root, you can say, “Well, it wasn’t in January you took that cocaine, it was February. You’re lying.”
In my case I expect they would discover that most of my boring old hair fibres are still oblivious to their age, several strands are coughing up pigmentation like a dying engine, while others have thrown caution to the wind and embraced a pigment-free lifestyle altogether.
– R.K. Finch
*For more on the work of Prof. Des Tobin, Professor of Cell Biology and Director of Skin Sciences at the University of Bradford, please visit www.skin.brad.ac.uk.