It might sound counterintuitive, but the chemicals in sunscreen that protect you from UV rays are themselves susceptible to sun damage. The only sunscreens that don’t break down when exposed to the sun are the physical ones—zinc oxide and titanium dioxide. Whatever type you choose, sunscreen should be the number-one part of your beauty regimen. If you use chemical sunscreens, remember that you must reapply every two hours you’re out in the sun.

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