How (and When) to Use AHA In Your Skincare Routine, According to Dermatologists

AHAs (alpha-hydroxy acids) are one of three groups of common chemical exfoliants, along with beta-hydroxy acids and polyhydroxy acids. AHAs are typically the most lauded for improving skin, and dermatologists recommend them frequently for a variety of skin concerns. Below, dermatologists discuss the best AHAs for dry skin, why AHAs deserve a place in your beauty routine, and how to use them for the best results.

What Are Alpha-Hydroxy Acids?

Alpha-hydroxy acids are a group of acid compounds, most often derived from plant-based sources. There are a variety of different ones out there, some of the most common of which include: glycolic (derived from sugarcane), lactic (derived from sour milk), citric (derived from lemons), and malic (derived from apples).

While they all act on the skin's surface as chemical exfoliants, they differ in size, penetration, and potency. "The smaller the molecule, the deeper the penetration, and therefore, the more efficacious it is," explains Nussbaum. However, on the flip side, increased efficacy can also mean an increased likelihood of irritation, particularly if your skin is already sensitive, to begin with. That's why the type of alpha-hydroxy acid you choose, its concentration, and the product it comes in are all essential, but more on that in a minute.

Benefits of Alpha-Hydroxy Acids for Skin

By definition, any type of acid is going to exfoliate the skin, but AHAs go above and beyond that call of duty. Here are more benefits of AHAs.

• They're a surface exfoliant: As skin cells die, they can often clump together and get stuck on top of the skin. Alpha-hydroxy acids dissolve the "glue" that holds them together, helping them to gently slough away, says Nussbaum. The result? Pretty much all of the things you want, namely increased radiance, a smoother texture, and fewer dark spots. This chemical exfoliation is what makes AHAs a good choice for those with sensitive skin, for whom physical exfoliation (AKA manual scrubbing) may result in redness and inflammation, Nussbaum adds.
• Increase collagen production: AHAs don't just work on the epidermis; they can also have effects on the deeper layer of the skin (or the dermis). "Studies show that all of the AHAs promote collagen development to a certain extent; however, none more than glycolic acid," explains Nussbaum, who adds that this is the AHA most often found in anti-aging products. And more collagen equals fewer lines and wrinkles.
• Hydrate: Glycolic acid, malic acid, and lactic acid are humectants, meaning they attract water to the skin. Lactic acid, in particular, is a top choice for those with dry skin, says Nazarian.
• Offer antioxidant benefits: Among the AHAs, citric acid, in particular, stands out for its antioxidant properties, making it a great pick for fighting free radical damage and lightening dark spots as well, Nazarian says.

Alpha-Hydroxy Acids vs. Other Acids

Generally speaking, AHAs tend to be overall less likely to cause irritation than BHAs. They also have slightly different benefits: "BHAs are better at decreasing oil production, so they're great for acne-prone skin, but are more aggressive than AHAs," explains Nazarian. Meanwhile, PHAs are much larger molecules than even the biggest AHA. As such, they are the least irritating of any acids out there but, at the same time, the least efficacious.

Side Effects

"Everyone should be diligent in finding the right concentration and right combination of AHAs for their skin type," advises Nazarian. "Overuse, or using a concentration that's too high, can lead to irritated and inflamed skin and flare other underlying conditions such as rosacea and eczema." Also worth noting: AHAs make your skin more sensitive to sunlight, so be extra diligent about applying sunscreen daily and re-applying every two hours, advises Nussbaum.

How to Use It

First, consider which alpha-hydroxy acid you want to go with. "Glycolic is the smallest of these acids and yields the most significant results," says Nussbaum. If you're sensitive, ensure you're using a low concentration; higher concentrations are best reserved for those with normal to oily skin, adds Nazarian. Lactic acid is a larger molecule, a good pick for sensitive skin, while malic acid is even larger and possibly less likely to cause irritation.

Still, a good rule of thumb is to choose a product that blends lower amounts of several different types of AHAs rather than using a super high dose of just one. "While a high potency of any one acid can yield significant results, combining different acids at lower strengths may be less irritating because they penetrate at different depths and offer different hydrating abilities," Nussbaum explains.

The type of product matters, too. You'll find AHAs in everything from cleansers to creams, but "those with sensitive skin should first start with wash-off formulas to minimize exposure to the active ingredients," recommends Nazarian. And, of course, it's imperative to follow the directions of the product you choose. Start slowly and gradually build up the frequency of use as tolerated, never exceeding what the instructions recommend.

Both the Byrdie team and Nussbaum recommend this overnight serum, which nabbed 'Best Chemical Exfoliator' in our 2019 Byrdie Skincare Awards. "The lactic acid in the formula sloughs away dead skin cells and keeps your complexion looking polished," says Nussbaum. It's fairly gentle, but if your skin is super sensitive, try using it as a mask and rinsing off after three minutes; you'll still see the amazing effects.

Given that the skin around your eyes is the thinnest and most delicate on the body (and the most susceptible to showing signs of aging), you'll want to treat it with extra TLC. Enter this eye cream. "It contains alpha-hydroxy acids to gently remove dull surface cells, and vitamins A, B, and C to decrease dark circles and fight aging free radical damage," says Nazarian.

Both derms we spoke with call out this serum. "I especially like this product for dry skin because both the lactic acid and squalane can help improve the hydration and texture," says Nazarian. Nussbaum also lauds it for being gentle: "It’s formulated at the optimal pH to provide overnight exfoliating results, while still being gentle enough to use nightly for most skin types."

True to its name, Nazarian likes this for oily and acne-prone skin. "This contains eight percent glycolic acid and works like a daily toner," she says. Oil- and fragrance-free, it's choice for helping to brighten skin and fade the telltale marks old blemishes can leave behind.

If you have sensitive skin, you can still use glycolic acid, but it's a good idea to first try it in a wash-off formula, like this cleanser. It's one that Nussbaum often recommends: "The formula gently exfoliates and brightens with glycolic acid and phytic acid, and calms the skin with aloe leaf juice."

"This serum is super lightweight, easy to apply, and is good for addressing anti-aging concerns such as tone and texture," says Nazarian. Credit glycolic acid, which does all of that, as well as helps minimize the look of fine lines and wrinkles.