Fact #5: Don’t skimp!
If you’ve been carting the same tube of sunscreen in your beach bag since last summer, we have news for you: You’re not applying nearly enough to get the SPF protection level listed on the tube. “To ensure you get the full SPF of a sunscreen, you need to apply 1 oz.—about a shot glass full,” says Dr. Kauvar. “Studies show that most people only apply one-half to one-quarter of that amount, which means the SPF they’re actually getting is lower than advertised.”

Think of it this way: If you have an 8 oz. tube of sunscreen, that’s eight applications. That tube should last you two or three trips to the beach, max—not the whole summer, and certainly not two summers in a row!

Fact #6: Reapply, reapply, reapply!
Okay, so we already mentioned this in Fact #3—but it bears repeating. No sunscreen in the world is going to keep you protected unless you’re diligent about reapplying every two hours. It can be tricky during the workday (who wants to slather additional sunscreen on top of their makeup?) but there are ways to get the protection you need without disturbing your foundation and concealer. Brush-on powder sunscreens can be swiped on right over your makeup to help boost your SPF before you head out for your lunch break.

A powder sunscreen to try:
Chantecaille Protection Naturelle SPF 46, $70

Looking for something a little stronger? Try: Chantecaille Ultra Sun Protection SPF 50, $80

MORE: Natural Sunscreens: More Pros Than Cons

For more ideas, check out these 27 skin-saving sunscreens.