The Scientist: Leslie Baumann, M.D., board-certified dermatologist and CEO of Baumann Cosmetic & Research Institute in Miami, FL.

The Answer: If you wear makeup with an SPF rating, your instincts are good, but it’s not going to get you the results you want (or need).To get sufficient sun protection, you need 2 mg of sunscreen per square centimeter of skin, which—based on the concentration of sunscreen in foundation—works out to seven times as much as you would normally wear. If you use powder, it’s 14 times as much! Think of it this way: The amount of powder you’d need to get proper sun protection is equivalent to the volume of a stack of 15 quarters, which pretty much means you’d have to use most of a container all at once.

On top of that, the pigment in makeup actually breaks down chemical sunscreen. The sun has the same effect, which is why you’re supposed to reapply sunscreen every two hours. Are you reapplying your makeup that often? We didn’t think so.

This isn’t to say that makeup with SPF doesn’t do anything. Indeed, almost all foundations are made with physical sunscreens (zinc oxide or titanium dioxide), which don’t break down in the sunlight. But again, it’s all about the amount, which is paltry—meaning that the SPF label on makeup bottles gives a false sense of security. In fact, FDA rules may soon require that foundations remove those SPF claims altogether, because they’re so misleading.

Bottom line? Wear sunscreen every day, and never rely on your makeup to do the job on its own.

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