Pigment-producing cells add colour to our hair as it grows. As we age the pigment-producing cells slowly die off and individual hairs appear white. When mixed in with strands of hair that still have their original colour, hair looks grey.
We can go grey whatever colour hair we have, however grey hairs tend to be much more noticeable in darker hair as darker hair has more pigment than lighter hair.
Most people begin to notice that they have grey hair by the time they turn 40, although grey hairs can appear when people are in the teens or twenties.
A study in 1996 showed that smokers are more likely to go grey prematurely than non-smokers. Werner syndrome (a rare disorder where sufferers age prematurely) and pernicious anaemia (a type of autoimmune anaemia) can also cause premature greying.
We can go grey whatever colour hair we have, however grey hairs tend to be much more noticeable in darker hair as darker hair has more pigment than lighter hair.
Most people begin to notice that they have grey hair by the time they turn 40, although grey hairs can appear when people are in the teens or twenties.
A study in 1996 showed that smokers are more likely to go grey prematurely than non-smokers. Werner syndrome (a rare disorder where sufferers age prematurely) and pernicious anaemia (a type of autoimmune anaemia) can also cause premature greying.