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Why does some hair change color when exposed to the sun? We checked archives in biology and general science.

This is a good question for a chemist but I'll try and give you a partial answer. Hair contains pigments that are vulnerable to chemical modification by a process called photobleaching. Rearrangements in the pigments molecular structure changes the way light is absorbed and reflected. A similar effect can be caused by chemical bleaching by the hair stylist or from chlorine in a swimming pool by a process called chemical bleaching. The sun may also change the water content of the hair and this can cause subtle color changes by changing the relative density of the color pigments. Try the chemistry board for a more complete answer. Don't let your roots show!
Michael B Lomonaco

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