By now you know the drill: Every few months a new wunderkind skin care ingredient is discovered in some remote locale, and pretty soon it’s everywhere—in your masks, serums, foot creams, insert-step-in-your-beauty-routine-here. But at the end of the day, there are only a handful of ingredients that have stood the test of time and truly become essential. “In skin care, they’re the holy grail,” says Cambridge, Massachusetts, dermatologist Ranella Hirsch.
You’ve probably heard of all these by now. (Retinol, hyaluronic acid, AHAs, peptides, and vitamin C all make the list.) But you may still be a little confused on what exactly each one does—and how you should be using them. Here, I break it all down.
Retinol: For Softening Wrinkles and Fighting Acne
If there’s one ingredient lauded more than any other for its wrinkle-fighting, complexion-perfecting abilities, it’s this derivative of vitamin A. “Here’s the deal with retinol,” explains Hirsch. “We were talking about it in 1975, and we’re still talking about it now because it works.” In study after study, retinol has been shown to build collagen, decrease fine lines, improve skin’s texture, and fight acne.
The prescription version (retinoic acid, or Retin-A) acts fastest, but it’s pricey—and it can be drying. Over-the-counter retinols take eight to 10 weeks to show results (compared with six weeks with an Rx), but are normally paired with anti-inflammatories to calm the redness, peeling, or dryness; they can also cost less than a prescription, depending on your insurance, generally starting around $100.
Whichever type you use, you’ll want to ease into your retinol use slowly. “I start patients on the mildest version, one night a week at the onset,” says New York City dermatologist Amy Wechsler. As your skin begins to tolerate a pea-size amount, you can eventually go up to two nights a week. But stay off harsh physical scrubs and peels while you’re using retinol; remember to moisturize, moisturize, moisturize; and use extra sunscreen for the first six months.
Hyaluronic Acid: For Serious Moisture
This tiny molecule helps lubricate joints and keep skin plump, and is one of the world’s finest humectants (elements that attract and retain water). What does that mean for skin? “Hyaluronic acid is awesome,” says Wechsler. In addition to being a terrific moisturizer, she says, it partners well with other active skin care ingredients (so you can layer it with retinol, for example, and use it daily). “The beauty of hyaluronic acid is that it doesn’t have any fine print,” says Hirsch. “It benefits any skin type, at any age. And the truth is that everyone looks great with hydrated skin.”
Vitamin C: For a Glow Boost
Doctors love vitamin C because it’s an incredible antioxidant and it stimulates collagen production—in other words, it increases glow and evens out spots. For best results, look for a high concentration, up to 20% in a serum or cream.
Vitamin C does have a downside, though: It breaks down when exposed to oxygen and light. Seek out truly airtight packaging, watch out for discolored formulas, and know that because vitamin C loses efficacy in the sun, it’s best as a nighttime product, says Montclair, New Jersey, dermatologist Jeanine Downie. But “use it on the nights you’re not applying retinol,” she adds. It’s also great in an eye cream to help soften fine lines and spots.
Peptides: For Firming
“Think of peptides as Legos—they’re protein building blocks,” says Hirsch of the skin strengtheners. Studies show certain peptides can boost collagen production and speed wound healing; or they can mimic the effect of Botox when applied topically. That means you’ll likely want to introduce peptides in your 30s, when you notice your skin doesn’t feel quite as firm or bouncy as it did in your 20s. They can also be used on your body to smooth and firm skin, and they may fade old scars and stretch marks. There’s emerging science that some peptides have been found to safely treat eczema.
Salicylic Acid and Benzoyl Peroxide: For Eradicating Acne
Okay, these are technically two ingredients—but the pair is name-dropped so frequently in the same acne-fighting sentence that it seems a shame to split them up.
“Salicylic acid is a lipid-soluble acid, so it penetrates into oily pores to clean them out, and it’s anti-inflammatory too,” renowned dermatologist Fredric Brandt once told us. “Benzoyl is antibacterial, so together they work synergistically.”
Look for bacteria-zapping benzoyl peroxide in face washes or spot treatments. It’s widely available in drugstores, ranging from 2.5% to 10% concentrations. (To minimize irritation, start with the lowest.) Try salicylic acid in an allover toner or cream to prevent breakouts, or on pimples if you have sensitive skin—it’s gentler than benzoyl, explains Wechsler.
Alpha Hydroxy Acids: For Smoothing
“My patients love, love, love AHAs,” says Downie, who explains that the powerful exfoliators are genius for clearing up sun damage, hyperpigmentation, acne, and fine lines. Multiple AHAs exist, but the most popular (and potent) is glycolic acid, which penetrates damaged skin to spur fresh, new skin cell production. Glycolic acid does its exfoliating work in everything from once-monthly in-office face peels to nightly washes, but it’s best not to use glycolic acid while you’re on retinols. And if your skin is sensitive, try glycolic’s less intense AHA cousin, lactic acid, which also chemically exfoliates but isn’t as drying.