Last month, while studying vitiligo (a condition in which the skin loses pigment in patches), European researchers discovered a piece of the explanation for why hair turns gray. Every hair cell makes hydrogen peroxide, and, over time, the amount accumulates, eventually blocking the synthesis of the normal pigment of the hair. This article points out that the role of other factors, such as stress (still considered folklore) and heredity, are yet to be determined. A major study in Sweden found no link between premature graying and shorter lifespan.