So many reasons: Sun exposure contributes to break down of elastic tissue and collagen in skin leading to skin wrinkling prematurely. It also causes pigmentary changes: freckles, solar lentigos referred to as "liver or age spots" and is a major contributor to skin cancer and precursors to skin cancer (actinic keratoses) sun avoidance and sun precautions (sun screen, protective clothing) is best for youthful skin.
Answered 10/4/2016
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