We’ve spent plenty of time roaming through Ulta and Sephora (in addition to the hours spent scrolling through their digital counterparts), and we can confirm there are zillions of products on the market that contain SPF. The trend goes past foundation and tinted moisturizer, veering into a whole new realm of lip balm and lipstick, finishing powder and even face mists. Don’t get us wrong, this excites us just as much as you telling your dermatologist you wear face sunscreen daily, but it leaves us a little skeptical, too. If you’ve found yourself wondering if the SPF in your makeup is enough to protect your skin from the sun, look no further. We reached out to NY-based dermatologist Hadley King, MD, for her expert opinion on the subject.You Need a Shot Glass of Product to be Protected“An important issue to consider when using moisturizers, primers and makeup with SPF is how much you need to apply to achieve the advertised SPF,” King explains. “You should use approximately 2 mg of product per square centimeter of skin. In practice, this means applying the equivalent of a shot glass of sunblock to the exposed area of the face and body — a nickel-sized dollop to the face alone.” We recommend an easy-to-blend formula like La Roche-Posay Anthelios Melt-In Sunscreen Milk SPF 60 and EltaMD UV Clear Broad-Spectrum SPF 46.If You Can’t Use a Shot Glass of Foundation, Re-Consider Your Options“If you don't feel that you can use this much of a product like tinted moisturizer, then you may prefer to use this much primer with SPF and then use a smaller amount of makeup,” Dr. King explains. Two of our favorite SPF makeup primers are Urban Decay Urban Defense Complexion Primer Broad Spectrum SPF 30 and La Roche-Posay Anthelios Daily Mineral SPF 50 Primer.Be Sure to Reapply Every Two HoursWe get it — it’s not easy to reapply sunscreen when you’re wearing makeup. But an easy way to do so is with a mineral powder sunscreen that doubles as a setting powder, like Brush On Block. Because it’s transparent, your makeup will stay perfectly intact. There are also makeup refreshing sprays with SPF like Supergoop Defense Refresh Setting Mist andCoola Makeup Setting Spray SPF 30.Read More:5 Non-Comedogenic Sunscreens That Won’t Clog Pores or Leave Skin GreasyThis All-In-One Water Gel Sunscreen Is a Must-Have In My Summer Beauty Routine5 Sunscreens That’ll Help Set Makeup