If you think you have gone grey from the stress of your job, family or relationship you could be right.
Scientists have found stress really does make you a silver fox, like George Clooney or Philip Schofield.
It has been argued that going grey early is an inevitable genetic process that runs in families.
But researchers found that when the body gets stressed - such as by serious illness or from some other shock - this has a dual effect.
As well as our immune system mounting a defensive response, it also triggers changes in the cells in hair follicles which produce colour.
For example, TV presenter Philip Schofield has said he first started going grey at 16. George Clooney said he first started going grey at 33
This in turn makes our hair turn silvery or grey.
Researchers from the University of Alabama, Birmingham found the ‘surprising’ link between genes that control hair colour and genes that signal to our bodies it is time to fight off an infection.
As well as ‘turning off’ hair colour, it can also turn off colour in the skin - leading to the disease vitiligo, of which pop star Michael Jackson was a famous sufferer.
The research - carried out on mice - published in PLOS Biology reports when the body is under attack our cells produce chemical signals called interferons.
These interferons make our cells’ machinery undergo changes that thwart viruses and generally boost defences.
But the unexpected side effect of the defence system is that it turns off cells that produce hair colour.
Grey hair is hair without