Skin care is a science (which, TBH, was not our best subject in school). The ingredients in our products might as well be in another language, and half the time we can't even pronounce them. We know the necessary essentials — cleanser, serum, eye cream, SPF, and moisturizer — and that it helps to know one's skin type. But short of donning a white lab coat and goggles, how do we create the perfect concoction of ingredients and formulas to get the desired result?Consider this an intro course to skin-care cocktailing. With the help of dermatologist Joshua Zeichner and aesthetician Christine Chin , we identified which ingredients are a match made in heaven and which can lead to nasty side effects when combined. So if we keep an eye on labels, and/or reach for made-to-mix products like the new Clarins Boosters to get the best results, we'll be sure to ace this skin-care test.