Gray hair refers to the phenomenon that part or all of the hair turns white. It can be caused by physiological factors, heredity, disease or mental factors. Clarifying the cause of the disease has a certain guiding role in treating white hair. Hair tends to turn white from the sideburns on both sides. At first, there are a few white hairs, and then the white hairs gradually increase and slowly develop to the top of the head; Old people not only have white hair, but also eyebrows, beards, armpit hair and pubic hair. The age, range and degree of gray hair vary greatly among individuals, which may be related to genetic, nutritional, spiritual and environmental factors.