Why does our hair turn grey?

Hair colour is produced by cells called melanocytes which create pigment that’s incorporated into growing hair fibres. Human hair growth is cyclical and pigment production turns on and off in rhythm with the hair cycle. When pigment cells turn off at the end of a hair cycle and fail to turn back on, hair becomes grey.

So, why doesn’t pigment production turn back on?

At the end of each hair cycle, some melanocytes become damaged and die. If the melanocyte reservoir at the top of the hair follicle can replenish the growing hair bulb pigment production continues.

But when it’s exhausted pigment production stops and the hair turns grey.

Genetic factors appear to be important in determining when we turn grey but there’s no evidence to link greying to stress, diet or lifestyle.