Loss of pigment. With age the pigmentvcells in the hair slow down and stop producing pigment. The effect is variable at what age this starts. There is a, variation with natural hair color and probably with the degree of processing that the hair has undergone.
Mostly. Genetics and stress.
Graying of hair is. related to genetic predisposition. Age of initial graying is largely a matter of genetics. However stressors: nutritional deficiencies, chemotherapy, traumatic head injuries, low vitamin B levels, zinc deficiency, severe illness, surgery & marked emotional stress may impact earlier depigmentation in people who are already predisposed to gray hair. Aging is a significant factor. In general –