This is a question we get asked a lot. It always surprises me because I thought the answer was something we were all taught and was well settled: after, of course. But after speaking with different dermatologists and reading different articles, I now see why there is such confusion. Apparently, there is a difference of opinion among the experts.First, Dr. Melda Isaac, a board-certified dermatologist based in Washington, D.C., says a good rule of thumb is “cleanse, medicate, moisturize, protect.” She believes that sunscreen will be diluted or degraded if put on before or mixed with moisturizer and as such should be applied after your moisturizer.In her opinion, sunscreen should be the last step in your daytime skincare routine, especially if you’re using a physical or mineral sunscreen, which works by physically blocking the UV rays.This step becomes more tricky when you’re using a chemical sunscreen, however.According to board-certified dermatologist Dr. Heather Rogers: “Chemical sunscreens have to be absorbed into the skin to be effective, so applying after your moisturizer will delay and hinder that. However, if you apply your chemical sunscreen before your moisturizer, your moisturizer will not work as well either because the skin is coated with chemical sunscreen.”So, to get around this, Dr. Rogers always recommends using a physical sunscreen with zinc and to apply it after your moisturizer. “Zinc is safe, effective, and provides the broadest protection against UVA and UVB rays.”“Generally speaking, the ingredients in a chemical blocker need to be absorbed into the skin so that they can do their job,” says Joshua Zeichner, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City. In other words, chemical SPF first. “You do not want anything that will interfere with their penetration” – like a thick moisturizer that will create a barrier between your skin and the SPF meant to protect it, Zeichner says. In this case, cleanse, medicate, protect, and moisturize would be the correct order. What’s the answer? Before or after moisturizer? The answer surprised us too: it depends. If you’re using a chemical sunscreen, before. If you’re using a mineral sunscreen, after. The only exception to this rule seems to be for those who put on moisturizer and let it completely absorb into the skin for fifteen minutes and then apply a chemical sunscreen. Most of us aren’t likely to do that, or at least not on a consistent basis. My opinion is the more sunscreen the better. Layer it up and layer all kinds. I know I’m in the minority though, so the type of sunscreen you choose seems to be important in this decision.Chemical before, mineral after. There, now it really is settled.