A lot of skin care is straightforward: Cleansers cleanse, moisturizers moisturize, and so on and so forth. But facial serums have been known to send those unfamiliar with skin-care specifics to Google, where they'll find this horrible (and, for these purposes, inaccurate) definition for the word: "an amber-colored, protein-rich liquid that separates out when blood coagulates," named after the Latin word for "whey," which is the liquid that remains after milk has been curdled and strained during the cheese-making process. Blood, milk water, curdling, coagulation — who needs any of that in their beauty routine, except maybe for casomorphin-addicted vampires?
But we've come a long way since... whey, and Elizabeth Báthory died in 1614 (coincidentally, around the same time the word "serum" was first coined). Serum is now used to describe an entire category of skin-care products; sometimes water-based, sometimes more of an oil, always something that dermatologist Joshua Zeichner, MD, describes as "a delivery system for highly concentrated active ingredients." And you — yes, you — need one, or three. Sure, a moisturizer will do its job to hydrate and protect... but your serum is what does the thing you need.
If all you've ever known is the rote three-step system you were once prescribed at a department-store cosmetics counter with your mom peering over your shoulder, maybe serum is not something you have considered adding to your routine. But listen, and listen good: A routine void of serums is a huge missed opportunity for skin improvement. "Moisturizers address skin hydration, but serums can do a variety of different jobs depending on what ingredients they're formulated with," says Dr. Zeichner. "Some help lighten dark spots, some improve the appearance of wrinkles, some offer antioxidant benefits — a serum complements your other skin-care products and can be layered underneath them."
At the end of the day, if you want to see real results, do this: Wash your face. Dry your face (gently, very gently). And while your skin is still a little damp, just before you moisturize, smooth on a few drops of your serum, like the ones Dr. Zeichner suggests ahead. Yes, it's your serum now, and you'll never want to be without it again. Hell, you might even want to bathe in it — you know, Báthory-style.