Science, Tech, Math › Science Why Does Hair Turn Gray? The Science of Gray Hair Share Flipboard Email Print Gary John Norman/Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated February 05, 2018 Have you ever wondered why hair turns gray as you get older and whether there is something you can do to prevent graying or at least slow it down? Here's a look at what causes hair to turn gray and some of the factors that affect graying. A Turning Point for Your Hair The age at which you'll get your first gray hair (assuming your hair doesn't simply fall out) is largely determined by genetics. You'll probably get that first strand of gray around the same age your parents and grandparents started to go gray. However, the rate at which the graying progresses is somewhat under your own control. Smoking is known to increase the rate of graying. Anemia, generally poor nutrition, insufficient B vitamins, and untreated thyroid conditions can also speed the rate of graying. What causes your hair's color to change? That has to do with the process controlling the production of the pigment called melanin, the same pigment that tans your skin in response to sunlight. The Science Behind the Gray Every hair follicle contains pigment cells called melanocytes. The melanocytes produce eumelanin, which is black or dark brown, and pheomelanin, which is reddish-yellow, and pass the melanin to the cells which produce keratin, the chief protein in hair. When the keratin-producing cells (keratinocytes) die, they retain the coloring from the melanin. When you first start to go gray, the melanocytes are still present, but they become less active. Less pigment is deposited into the hair so it appears lighter. As graying progresses, the melanocytes die off until there aren't any cells left to produce the color. While this is a normal and unavoidable part of the aging process and is not of itself associated with disease, some autoimmune diseases can cause premature graying. However, some people start going gray in their 20s and are perfectly healthy. Extreme shock or stress can also cause your hair to go gray very quickly, though not overnight.