Are You Using Your Exfoliating Acids Wrong?

Photo: Kate Anglestein
You don't have to be a professional esthetician to get your hands on acids anymore — the same potent ingredients that were once considered too potent for at-home use are now a mainstay of our bathroom shelves. Sephora has over a thousand products containing the word acid; Ulta Beauty has nearly 500, and they can all be shipped to your home with just a few clicks of the Add to Cart button. But are they as safe and beneficial for everyone as the product description insists?
First things first: It's important to understand the distinctions between acids, because they are not all made alike. "There are different kinds of acids used in skincare, and some are very beneficial," says celebrity facialist and dermatologist Dr. Barbara Sturm, who launched her own eponymous skin-care brand in 2016. "For example, hyaluronic acid, which helps refill the skin's moisture reservoirs due to its very high ability to bind water. It's a natural component of our skin, and its production diminishes with age, but we can replenish it through topical application or supplemented oral intake."
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And then there are AHAs (alpha-hydroxy acids) and BHAs (beta-hydroxy acids). "All acids have an exfoliating effect, but AHAs can be used by all skin types, while BHAs are good for people with problematic skin as they have an antibacterial effect and prevent clogged pores," says Lixir Skin founder Colette Haydon. "Each acid offers a special benefit: Lactic acid improves hydration, lactobionic acid reduces oxidative stress (which makes your skin look dull and grey), and phytic acid eliminates heavy metals to detoxify the skin. Salicylic acid is antibacterial and prevents clogged pores, and azelaic acid controls sebum."
When there are so many options, how do we know what will work for our skin type? Should someone with sensitive skin be using their acid of choice as much or in as high a concentration as someone with dry skin? And does age play into it at all? "The 'good' acids like hyaluronic acid or citric acids support the skin with moisture, strong anti-oxidative effects, and other valuable benefits," Dr. Sturm says. "The acids that damage the skin, however, cause a serious disruption of its protective barrier and often cause dehydration. They accelerate the cell renewal and cause a long-term effect of the skin thinning out, as the cells cannot divide infinitely. This affects all skin types, but someone with very sensitive skin might suffer a faster negative response, which could lead to serious cases of hyperkeratosis."
While this sounds scary, rest assured that the acids you'll find on the market are largely regulated. "The critical point is the concentration used on our skin," says Dr. Mirela Mitan, CEO and founder of MMXV INFINITUDE. "The safety level in cosmetic products is if the concentrations are lower than 10% at final formulation (pH > 3.5) and when formulated, to avoid increasing sun sensitivity or to be used with daily sun protection. When applied by trained professionals, in beauty salons, the AHAs are safe at concentrations less than 30% at final formulation and a pH higher than 3. If applied according to a dermatologist's recommendation, an even higher concentration of AHA preparation could be considered safe to use."
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So once you've found a good acid that works for your skin type, and made sure it's lower than 10% in concentration and above 3.5% pH level, the next step is making sure you apply it properly. "It’s very important to only apply acid at night and never use it on holiday when you’re exposed to the sun," Haydon warns. (Of course, you should wear SPF every day when using acids no matter where you are.)
If you think your skin is too sensitive, or you've had bad reactions in the past but still want that dullness-blasting exfoliation, there are alternatives to acids. "Vitamin C, or L-ascorbic acid, is an acid, but it’s not an AHA, so it won’t exfoliate your skin and will just give you a magic 'quick fix' of radiance," Haydon says. "It’s a wonderful ingredient, one of the most active of them all, and is increasingly beneficial to your skin with continued use."
Dr. Mitan has another suggestion: an alternative to AHAs called PHAs, for polyhydroxy acids, and bionic acids, which have similar effects to AHAs without the possibility of skin irritation," she explains. "PHA is more compatible with sensitive skin, has better moisturization activity, and enhances skin barrier function." So whether you stick with the popular acids in your skin-care routine, or you give their gentler alternatives a try, there are countless ways to get the glow this winter.

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