Everything You Need to Know About Serums

Facial serums are flooding beauty aisles everywhere. Sure, they feel lovely, but we asked dermatologists if the extra step is really worth your time and investment.

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Q: What exactly are serums?
A: “They’re lightweight, fast-absorbing liquids that are concentrated with a specific active ingredient, including antioxidants, like vitamins C or E, glycolic acid, caffeine, or peptides, and are designed to deliver high levels of these ingredients directly to the skin,” explains Dr. Joshua Zeichner, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City. Because they don’t contain oil—serums are about 90 percent water—they don’t leave a greasy residue behind.

Q: How do you incorporate them into your routine?
A: “Use one directly after cleansing, but before applying moisturizer, sunblock, or foundation,” says Dr. Neal Schultz, founder of DermTv.com and creator of BeautyRx. “When one applies skincare, go from lightest to heaviest.” As for morning or nighttime use, antioxidants should actually be applied at bedtime because they work best when not competing against sunscreen. The same goes for glycolic acid and retinol, since these ingredients can make your skin sensitive, especially when exposed to the sun. A little serum goes a long way; a pea-size amount is enough for your full face.

Q: Who needs them and how do you determine which one is best for you?
A: “You’re never too young to use an antioxidant,” says Dr. Schultz. These ingredients help prevent free radical damage as well as help repair any damage already done. While most serums are good for all skin types, there are ingredients that work best for certain skin concerns. A helpful cheat-sheet:

  • Vitamin C helps brighten brown spots.
  • Glycolic acid smooths the skin’s texture, plus it reduces the appearance of large pores and fine lines.
  • Caffeine helps to firm skin and protect against free radical damage.
  • Hyaluronic acid, a molecule that holds up to 1,000 times its weight in water, offers hydration, great for those with dry skin.
  • Those concerned with fine lines should look for serums that contain retinol, peptides, or antioxidants.

If your skin is sensitive, try a test patch on a small area first, and try this pro application tip: Wait until your face is completely dry before applying a serum, since ingredients penetrate deeper on wet skin.

Q: What changes can you expect to see with consistent use?
A: “It depends on the product you are using, but in general, it takes only a few uses to increase hydration with hyaluronic acid compared to the weeks or even months it takes to brighten brown spots and improve the appearance of fine lines and wrinkles,” says Dr. Zeichner.

Check out some of our favorite serum picks here.