The answer is heredity. Acquired canities, gray hair that shows up as you age, is most often traced back to genetics.
Chemical over-processing, a scalp fungus, and vitamin deficiencies can all cause real hair problems, but they're not the usual source of age-related graying. "Acquired" here just means it developed over time rather than being present from birth — it doesn't point to an outside cause. Heredity drives it, the same way it drives most patterns of hair loss.
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