As it becomes steamier and stickier outside, many of us wrestle with the right way to moisturize our aging skin. Slathering on a rich cream worked well in mid-February, but that same product probably now leaves you feeling more gooey than dewy—and it may be causing your makeup to slip and slide around your face. Not good. My solution? On days that are super-soupy, I skip lotions and creams altogether and sub in a hyaluronic acid serum.