In so many DermTV episodes we’ve mentioned the importance of putting sunscreen on before other products but today I’m going to explain to you exactly why. Let’s first discuss traditional, regular, chemical based sunscreens; those are the ones where the active ingredients are carbon based chemicals. In the instructions it always says apply 20-30 minutes before going outdoors. The reason for that is it takes 20 or 30 minutes for the sunscreen to actually bind to the surface of the skin to form a chemical reaction that enables and activates the sunscreen chemicals to work. If, before you put your sunscreen on, you put any other product on, you’re going to interfere with the ability of those chemicals in the sunscreen to actually bind and do what they need to do to become activated. What happens if after your sunscreen you put on moisturizer? Certainly I’ve told you many times that every two or three hours or after you swim or sweat you need to reapply your sunscreen. What about the fact that you’ve already put moisturizer on? Well there’s a good chance that that moisturizer will be sweated off or come off while your swimming and in an ideal world, sure you’d wash your face again before you put your sunscreen on but it’s not an ideal world and reapplying your sunscreen several hours later will probably not be impeded by any moisturizer that’s left because there won’t be much left. Let’s talk about chem free sunscreens which are the physical blockers, they’re not really chemical free, they just don’t have carbon based chemicals, but they’re based on either zinc or titanium. They actually are physical blockers so a layer of that sunscreen prevents the sun even from penetrating and it bounces off. Since they’re physical shields, it really shouldn’t matter what order you put it, if there are products under it or over it. But the reality is, for it to work as promised and deliver the sun protection that is tested and labeled on the bottle, you really need to put it on the skin first again and that’s because if other products are put on first the other products will either not allow the sunscreen to form an even layer on the skin or may actually dilute the sunscreen so you’re just not getting the promised sun protection. So again, whether you’re using additional chemical sunscreens or chem free sunscreens make sure you apply your sunscreen first if you want to get the best sun protection.