Do you really need a serum?

Think of a serum as the powerhouse of a skincare regimen. "A serum is highly concentrated and has biologically active substances to help accomplish specific goals," says Catherine Orentreich, M.D., a New York City-based board certified dermatologist who serves as a guiding dermatologist for Clinique. Packed with potent and targeted ingredients, serums are generally on a single mission, whether it's to reduce dark spots, boost your glow, smooth fine lines, or tighten everything up a bit. A serum is also lighter and thinner than most moisturizers, which allows it to quickly penetrate into the skin and work on a deeper level.

Not really if you don't have any big skin gripes that are bugging you. But if you're bothered by a skin concern, like a relentless dark spot or little lines creeping up around your eyes, then adding a serum to your regimen is a good idea. Using a serum and a moisturizer that contain complementary ingredients is like a one-two punch on a skin issue: you'll see results faster. Together, they're the ideal support group for your skin.

In addition to all the potent problem-solving ingredients that are in a serum, it may provide a certain amount of hydration—but not enough to replace your moisturizer. Moisturizers also deliver a more well-rounded meal, containing other healthy ingredients that your skin needs beyond battling your primary concern. Lastly, serums don't have SPF because they are designed to go deep into your skin, while sun protection ingredients are designed to stay on the upper layers to deal with those harmful UV rays.

The rule of thumb when it comes to layering skincare: Go from thinnest to thickest. Serum first, moisturizer second. You can use the same serum morning and night, but switch up your moisturizers: a day cream with SPF and a night cream with more skin-repair ingredients.

It's not really about age, but the condition of your skin and any issues you’re concerned about. Thinking you need a power pair? Here's what to look for...

Start with a serum like Even Better Clinical™ Radical Dark Spot Corrector + Interrupter, which contains vitamin C, yeast extract, and salicylic acid to break up dark spots and reduce discoloration, while soothing gyokuro green tea, a potent antioxidant, quells irritation. "Salicylic acid is wonderful for promoting exfoliation," says Dr. Orentreich. Pair it with Even Better™ Skin Tone Correcting Moisturizer Broad Spectrum SPF 20, which contains similar ingredients, plus SPF to prevent future damage.