What is grey hair?
And is it actually coloured grey?
Well, no.
"It is hair with no pigment and the way in which the light has reflected that it looks slightly, slightly greyish in colour," according to Rodney Sinclair, Professor of Dermatology at Epworth Hospital at the University of Melbourne.
After every hair cycle, some of the pigment gets lost.
Melanocytes, which produce the pigment for growing hair fibres will usually replenish the colour, but when their reservoir of stem cells is used, pigment production stops and hair turns grey.
How many of us have grey hair?
"Of all the people walking around Australia about 75 per cent of them are grey or have certainly got some degree of grey hair," Professor Sinclair told the ABC's Fi Poole.
"And there is a huge industry, we've got 70,000 hairdressers in Australia ... and a lot of what they're doing is not just cutting hair but colouring hair, largely to conceal grey."
So is it a genetic thing?
Pretty much.
"The best evidence of that comes from identical twins, and when you look at identical twins they seem to go grey at the same age, same rate, same pattern," Professor Sinclair said.
"So that the genetic factors are really important.
"The problem we have is that we don't actually, we haven't yet identified what the controlling genes are [and] we don't understand the genetic mechanism of going grey but the genes and the hereditary of grey hair is a really striking feature."
And is it actually coloured grey?
Well, no.
"It is hair with no pigment and the way in which the light has reflected that it looks slightly, slightly greyish in colour," according to Rodney Sinclair, Professor of Dermatology at Epworth Hospital at the University of Melbourne.
After every hair cycle, some of the pigment gets lost.
Melanocytes, which produce the pigment for growing hair fibres will usually replenish the colour, but when their reservoir of stem cells is used, pigment production stops and hair turns grey.
How many of us have grey hair?
"Of all the people walking around Australia about 75 per cent of them are grey or have certainly got some degree of grey hair," Professor Sinclair told the ABC's Fi Poole.
"And there is a huge industry, we've got 70,000 hairdressers in Australia ... and a lot of what they're doing is not just cutting hair but colouring hair, largely to conceal grey."
So is it a genetic thing?
Pretty much.
"The best evidence of that comes from identical twins, and when you look at identical twins they seem to go grey at the same age, same rate, same pattern," Professor Sinclair said.
"So that the genetic factors are really important.
"The problem we have is that we don't actually, we haven't yet identified what the controlling genes are [and] we don't understand the genetic mechanism of going grey but the genes and the hereditary of grey hair is a really striking feature."
