The theory that you need to lighten up on the hydration front isn't a lie you've been told in order to sell more moisturizer. Bolder puts it this way: "Think of your moisturizer in a similar way to your clothes — lighter in summer, heavier in the winter." She also recommends adding a salicylic acid serum if you have oily or combination skin, to help exfoliate and clear out any dirt and bacteria that cleansing alone can't reach. And for all skin types, Bolder says weekly exfoliation is essential. "It's important to slough off that top layer of dead, dull skin that builds up thanks to the extra sweat, SPF, and pollution," she explains.