Black hair grows mainly by the formation of melanin cells at the roots of the hair. With age, the pigment cells at the root of the hair follicle will stop or reduce the production of melanin, and grey hair will be formed as a result. Duan Xingwu, director of the dermatology department at Dongzhimen Hospital, said that normal hair is black because there is melanin, melanin particles, and grey hair is because there are no more melanin particles. In addition, it is recommended not to forcefully pull out white hair. Although plucking white hair will not make it grow more and more, it will hurt the hair root, especially if it is plucked too much, it may also cause folliculitis.

　　When there are more grey hairs, many people will dye them. Experts say it's better to let nature take its course. Although there is no conclusive evidence on whether hair dyes cause cancer, hair dyes are after all chemicals and do have potential risks such as allergy, plus the scalp is closest to the brain, frequent exposure to chemicals can bring harm to other organs, especially those with low immunity should not dye their hair.

　　Duan Xingwu said, due to aging caused by grey hair is a normal physiological process, the possibility of reversible is very small. But some people will appear "less white head", its causes are many, part of the juvenile grey hair and hereditary, this reversible possibility is not very large; part of the mental and mood and other factors related to, and part of the nutrition, chronic diseases, these are reversible.

　　How to protect hair, try to avoid the production of grey hair? Experts suggest that the first relaxation to ensure that sleep; the second to moderate exercise, so that the blood circulation of the whole body; the third can be local massage hair; the fourth is to eat some food containing B vitamins and some with the colour of food, such as black beans, fungus, black sesame seeds, chasteberry and other foods.