Why you have to avoid or stay out of the sun if you want skin to stay younger?

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.