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Most sunscreens on the market are chemical, which means that chemicals in their formula actually prevent sun from hitting the skin by absorbing the rays. Physical sunblock, however, works by creating a physical barrier between the skin and the sun. Because the makeup won't allow your skin to absorb chemical sunscreen, it won't be effective protection. Physical sunscreen can still work over your makeup to deflect the sun's rays. Physical sunblocks come in powders, creams, and sprays, so choose whichever will be easiest for you to apply. Because your makeup is already applied, a spray sunblock will be your best bet to avoid ruining it. To apply it properly, close your eyes and hold your breath. Press down on the nozzle, and apply it by spraying back and forth over your entire face. Spray more than you think you need, because spray sunscreen don't cover quite as well as creams and lotions. Don't touch your face at all while the spray dries. If you touch it, you risk rubbing it off in spots and compromising the sun protection. Another spray option is a makeup setting spray with SPF. Like the spray sunscreen, this shouldn't be used as your only form of sun protection, but it's great for touch-ups and to help keep your makeup in place throughout the day. Not only do makeup setting sprays with SPF protect your skin from the sun, they can actually mattify and moisturize your skin at the same time.
Apply a physical sunblock over makeup. Use a spray sunscreen.