Whether or not you actually do it, you know that you should be wearing sunscreen all the time — not just in the summer. It is, without a doubt, the best thing you could do for your skin.
However, aside from that hard-and-fast rule, there are a lot of grey areas when it comes to SPF. How often should you reapply? What's the difference between chemical and physical sunscreens? Is the SPF in your makeup really enough?