Canities a.s.a.s. (grey hair) refers to natural ageing (from the age of 30-40 years). The gray appearance is caused by the gradual decrease of colored hair. Greying before the age of 20 (for dark skin before the age of 30) is called canities praecox (premature greying). Mostly e.c.i., sometimes familial, sometimes with rare syndromes (Böök syndrome, progeria, Rothmund, Werner).
Grey hair is caused by a decrease in the amount of pigment in the hair.
Hair color is determined by the amount of melanin pigment supplied to the hair and by the type of pigment: eumelanin or pheomelanin. Eumelanin is available as black eumelanin and as brown eumelanin. Pheomelanin gives the hair orange and red tones. Everyone has a certain amount of pheomelanin in their hair. A small amount of brown eumelanin gives blonde hair, a higher amount of brown eumelanin gives brown hair. A large amount of black eumelanin results in black hair, a small amount of black eumelanin results in grey hair. With increasing age, the production of melanin pigment decreases and grey hair is produced. When all melanin disappears completely, the hair becomes white (colourless). Real grey hair does not exist, it is always a mixture of discoloured (white) hair and the remaining black hairs, which together cause the grey colour.
The time of aging depends on age and hereditary factors. Some people go grey early, for example from the age of 25, others keep their original hair colour until old age. Premature greying can be hereditary. There are also racial differences. The first grey hairs often appear on the temples, in men in the beard hairs. Then it spreads to the rest of the head and body.
Grey hair develops with age, there is not really a cause. It may also be caused or rather accelerated by underlying factors such as poor nutrition (vitamin B12 deficiency), diseases (anaemia, cardiovascular diseases, autoimmune diseases, thyroid diseases), smoking and certain drugs (chloroquine).
Treatment is usually not desired, gray hair is considered to be something that comes with aging. Those who find it disturbing can camouflage it by dyeing their hair (colour shampoo, colour conditioner, hair colour). Not all hair dyes are suitable for colouring grey hair. You could pull out a few white hairs. There are hair care products that can camouflage the grey colour, for example by making the white hair more transparent. Colour conditioners give a layer of colour on the outside of the hair and are temporary, when the hair is washed, the colour is washed out again. Hair dyes have a permanent effect, but the growth of hair at the roots will eventually make your own hair colour visible again.