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Hairy situation: Scientists explain how stress-related graying occurs

Marie Antoinette's hair turned white overnight, according to folklore, before she was executed by guillotine in 1793 during the French Revolution. The ill-fated queen embodied an extreme example of the phenomenon of stress-induced graying of the hair. The biological mechanism behind such graying had long remained a mystery. But researchers said on Wednesday they have figured out how it happens: it is driven by the body's "fight-or-flight" response to danger.