1 Why do we go grey?
Asim Shahmalak said: "Cells called Melanocytes produce the melanin, or pigment, that gives both hair and skin its colour. Hair goes grey when the melanocytes slow down their production of melanin, and eventually they stop producing it altogether.
"As we age, our bodies stop producing so many melanocytes, and those we do have don't work as efficiently, so we will all go grey at some point."
2 What is the main cause of greying?
Dr Shahmalak said: "Genetics is the main cause. If your parents went grey early, the chances are that you will, too. This is a far more important reason than environmental factors. The younger you start going grey, the quicker you're likely to go from having a full head of coloured hair to being grey all over."
3 Are there any non-genetic factors which can accelerate greying?
Dr Shahmalak said: "Yes, ultraviolet light, air pollution and cigarette smoke are associated with the production of unstable compounds called free radicals in our bodies, which some experts believe destroy the melanocytes that give hair its colour.
"This theory was backed by a 1996 study which found that smokers were four times more likely than non-smokers to go grey prematurely."
4 Are you more likely to go grey if your hair is a particular colour?
Dr Shahmalak said: "No. Dark-haired people are thought to go grey earlier, but this is only because the grey hairs are more obvious. Blondes are the last to notice grey hair because of the subtler blending of white and blonde.
5 Can stress give you grey hair?
Dr Shahmalak said: "Possibly but genetics are far more important. We have all heard of people going grey overnight because of a bereavement.
"Researchers in New York found that melanin-producing cells disappeared when mice were exposed to stress hormones. These cells failed to return, turning hair permanently grey."
6 Does pregnancy accelerate greying?
Dr Shahmalak said: "There is no hard evidence that it does, though you hear lots of anecdotal evidence from women that pregnancy has turned them grey. There is no doubt that hormonal changes during pregnancy do affect hair. Some women report that it looks and feels thicker while others have complained their hair is dryer and needs extra moisture. Hormonal changes are different for each woman."
Dr Shahmalak performs FUE (follicular unit extraction) and FUT (follicular unit transplantation) procedures at Crown Clinic. He is well-known for his work with celebrities including actor Jack P Shepherd, model Calum Best, Homes Under The Hammer Presenter Martin Roberts and former footballer Didi Hamann who all had FUE procedures at Crown Clinic. TV doctor Christian Jessen had a FUT (follicular unit transplantation) procedure at Crown Clinic.