Why You Should Add Lactic, Citric, and Other Acids to Your Skin-Care Regimen

Glycolic and salicylic are common. But phytic acid? Tartaric? These lesser-known players can have a major impact on clarity and radiance. Meet the new standouts.

Photo: Eva-Katalin/Getty Images.

When glycolic acid was introduced in the early 1990s, it was revolutionary for skin care. Known as an alpha hydroxy acid (AHA), it was the first over-the-counter active ingredient you could use at home to accelerate dead-skin-cell sloughing and reveal the fresher, smoother, plumper skin underneath. Later we learned that the sugarcane derivative could also stimulate your skin's collagen production.

Then came salicylic acid, a beta hydroxy acid (BHA) that could dissolve sebum buildup deep inside pores and act like an anti-inflammatory, making it good for red, irritated, acned skin. (See: Is Salicylic Acid Really a Miracle Ingredient for Acne?) As a result, glycolic acid became the gold standard for antiaging and salicylic acid became an anti-acne darling. That remained largely unchanged until recently.

Now some skin-care products contain lesser-known acids like mandelic, phytic, tartaric, and lactic. Why the additions? "I think of glycolic and salicylic acids as the lead actors in a play and these other acids as the supporting cast. When they all work together, they can improve the production," says Shape Brain Trust member Neal Schultz, M.D., a New York City dermatologist.

These supporting players improve efficacy for two reasons. First, while most acids aid in exfoliation, "each does at least one additional beneficial thing for the skin," says NYC dermatologist Dennis Gross, M.D. These include boosting hydration, fighting free radicals, and helping stabilize a formula so it lasts longer. The second reason is that using multiple acids at a lower concentration (instead of one at a high concentration) may make a formula less irritating. "Rather than adding one acid at 20 percent, I prefer to add four acids at 5 percent to achieve similar results with less chance of causing redness," Dr. Gross says. (FYI, a combo of acids is the magic behind Baby Foot.)

So what specific benefits do these up-and-comers offer? We break it down:

Mandelic Acid

This is an especially large molecule, so it does not penetrate the skin deeply. "That makes it better for sensitive types because shallower penetration means lower risk of irritation," Dr. Gross says. Renée Rouleau, a celebrity aesthetician in Austin, says this AHA can also help "suppress the production of excess pigment." With one caveat. "Mandelic acid helps improve exfoliation and lower the risk of irritation when combined with glycolic, lactic, or salicylic, but it's probably not enough of a power player to exist in a product alone."

Lactic Acid

It has been around for a long time-Cleopatra used spoiled milk in her baths around 40 BCE because the milk's natural lactic acid helped slough away rough skin-but has never achieved glycolic-level fame because it's not quite as strong, which can be a good thing. Lactic is a large molecule, so it's an effective alternative for sensitive types, and unlike mandelic, it's potent enough to be a lead player in a product. Dr. Gross explains that lactic acid also bonds to the top layer of skin and stimulates it to make ceramides, which help keep moisture in and irritants out.

Malic Acid

Sourced primarily from apples, this AHA offers some of the same antiaging benefits as lactic acid, but "it's considerably more mild," says Debra Jaliman, M.D., a New York City dermatologist. When added as a supporting ingredient in a formula that contains stronger acids like lactic, glycolic, and salicylic, it aids gentle exfoliation and ceramide stimulation.

Azelaic Acid

Neither an AHA nor a BHA, azelaic acid, derived from wheat, rye, or barley, "has both antibacterial and anti-inflammatory properties, making it an effective treatment for acne or rosacea," says Jeremy Brauer, M.D., a New York dermatologist. It treats both by descending into follicles, killing any bacteria inside them and quelling the inflammation caused by infection. Azelaic acid can also "stop the creation of excess melanin responsible for dark spots, freckles, and uneven patches on the skin," Dr. Jaliman says. It's appropriate for darker skin (unlike hydroquinone and some lasers) because there's no risk of hypo- or hyperpigmentation, and it's approved for pregnant and nursing women. That's a huge plus because "so many women have issues with melasma and breakouts around pregnancy," Dr. Jaliman says.

Phytic Acid

Another acid that is neither an AHA nor a BHA, this outlier is an antioxidant, so it helps fend off skin-aging free radicals. It can also prevent blackheads and shrink pores. "Phytic acid works by gobbling up calcium, which is notoriously bad for the skin," Dr. Gross says. "Calcium converts your skin's oil from a fluid to a wax, and it's the thicker wax that builds up inside pores, leading to blackheads and stretching out pores so they appear larger." (This is everything you need to know about getting rid of blackheads.)

Tartaric Acid

This AHA comes from fermented grapes and is added to glycolic or lactic acid formulas to strengthen their sloughing. But its primary benefit is its ability to regulate a formula's pH level. "Acids are notorious for morphing pHs, and if they swing too high or too low in a product, the result is skin irritation," Rouleau says. "Tartaric acid can help keep things stable."

Citric Acid

Similar to tartaric, citric acid, an AHA found primarily in lemons and limes, also keeps other acids within a safe pH range. Additionally, it acts as a preservative, enabling skin-care formulas to stay fresher longer. Finally, citric acid is a chelator, which means it eliminates irritating impurities (from air, water, and heavy metals) on the skin. "Citric acid grabs onto these impurities so that they cannot enter your skin," Dr. Gross says. "I like to think of it as skin's Pac-Man."

Best Blends

Try these acid-containing products for a radiance boost.

  • Dr. Dennis Gross Alpha Beta Exfoliating Moisturizer ($68; sephora.com) boasts seven acids.
  • Drunk Elephant T.L.C. Framboos Glycolic Night Serum ($90; sephora.com) resurfaces while you sleep.
  • The Ordinary Azelaic Acid Suspension 10% ($8; theordinary.com) evens tone.
  • BeautyRx by Dr. Schultz Advanced 10% Exfoliating Pads ($70; amazon.com) smooths, brightens, and firms.
  • Dr. Brandt Radiance Resurfacing Foam ($72; sephora.com) gives skin a weekly dose of five acids.
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