So let’s start with the first category, shall we? Below, find everything you need to know about humectants, including how they work, how to use them, and the best options to slather on. “Think of the skin as an actual sponge,” adds Shamban. “When it is dry, it is thin, brittle, not pliable, rough in texture, dull, and sallow in color. Run it under water, and it is instantly plump, dense, and smooth. Even the color is brighter.” The humectants are what help usher that water into the “pores” of the sponge and hold it there, making the appearance plump and full of moisture. Essentially, humectants are attracted to water—but this can also backfire, specifically in arid environments. See, when the humidity is high, humectants have an easier time pulling in water from the outside air; but when that humidity dips, the humectants can actually pull water from the deeper layers of the dermis into the stratum corneum (or the outermost layer), which can leave your skin drier than before, as water can easily evaporate on the top layer of the skin. “The magnet forces are attracted to water pulling in or out of the dermis,” explains Shamban, so you want to make sure this water magnet is drawing in moisture from the surrounding environment, not from your own skin. Board-certified dermatologist Angelo Landriscina, M.D., seconds the advice: “The humectants in your products, like hyaluronic acid and glycerin, will have an easier time holding on to moisture if you’re providing it,” he says. Otherwise, those humectants will still do their job—they’ll just pull water from your skin instead of the surrounding air, which can leave it even drier than before. That said, follow these steps: Find our favorite HA serums here. Read all about glycerin and our favorite products here. Plus, it makes a winning face mask: Read up on all the benefits of this all-natural humectant, then check out these DIY hydrating face masks. AHAs in general are hydrophilic, meaning they’re water-loving, and in addition to increasing skin cell turnover and reducing the appearance of fine lines, they have also been shown to improve moisture content in the skin4. “They can be simultaneously exfoliating and hydrating, making them very beneficial to many skin types,” says board-certified dermatologist Mona Gohara, M.D.