18 year old with a few grey hair.. what does this mean?

Genetics: Our hair is generally preprogrammed by our genes to stop making pigment that gives it color. Rarely, a medical illness, stressors or medical treatments, like chemotherapy, can change our hair color or cause a lack of color(white or gray). Ask older relatives when they saw their first gray hair.

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 –