There are a variety of different acids commonly used in the skincare world. Take a quick look at the ingredients in any of the products you're currently using, and we're willing to bet there's some type of acid in at least one of them. And while all skincare acids share certain attributes—mainly that they all act as chemical exfoliants—by no means are they created equal. They're typically categorized into three groups: alpha-hydroxy acids, beta-hydroxy acids, and polyhydroxy acids. (More often referred to by their respective acronyms AHAs, BHAs, and PHAs). Among the three, however, there's no denying that AHAs reign supreme. Encompassing several different types of acids with an option for every skin type and complexion concern, they're lauded by dermatologists for far more than just their exfoliating prowess.
Meet the Expert
Keep reading to find out why alpha-hydroxy acids get an A+.
Type of Ingredient: Acid/chemical exfoliant
Main Benefits: Exfoliates the top layers of skin to minimize dullness and even out texture; some AHAs can also stimulate collagen production, while others have antioxidant and hydrating properties.
Who Should Use It: Given their wide range of effects, most people can benefit from using AHAs, says Nazarian, so long as you find the right alpha-hydroxy acid and concentration of it for your skin type.
How Often Can You Use It: This differs greatly based on the particular acid, product, and your skin. Follow product directions, but always start slow, using any AHA only once or twice per week and gradually increasing frequency as your skin can tolerate it, suggests Nussbaum.
Works Well With: Peptides can slow the penetration of AHAs, making them less irritating, says Nussbaum. You can also pair them with hydrating ingredients.
Don't Use With: Avoid using retinoids at the same time of day as AHAs, and be cautious when using both BHAs (beta hydroxy acids, such as salicylic acid) and AHAs in order to minimize irritation.
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 surface of the skin as chemical exfoliants, they differ in size, and subsequently 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 very important, 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.
- 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.
"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 can flare other underlying conditions such as rosacea and eczema." Also worth noting: AHAs do 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, make sure you're using a low concentration of it; higher concentrations are best reserved for those with normal to oily skin, adds Nazarian. Lactic acid is a larger molecule, a good pick for those with sensitive skin, while malic acid is even larger and therefore 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 amount 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.
The Best Products With Alpha-Hydroxy Acid
Nussbaum likes the blend of alpha-hydroxy acids (glycolic, lactic, and malic) in this wash, which are slow-released to gently exfoliate while minimizing the likelihood of irritation. It also delivers a boost of complexion-brightening oxygen, she says.
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.
What does alpha-hydroxy acid do to your skin?
Alpha-hydroxy acid exfoliates the top layers of skin to minimize dullness and even texture; some AHAs can also stimulate collagen production, while others have antioxidant and hydrating properties.
Does alpha-hydroxy lighten skin?
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.
Can I use alpha-hydroxy acid every day?
How often you use alpha-hydroxy acid depends on the particular acid, product, and skin. Follow product directions, but always start slow, using any AHA only once or twice per week and gradually increasing frequency as your skin can tolerate it.
Tang SC, Yang JH. Dual effects of alpha-hydroxy acids on the skin. Molecules. 2018;23(4):863. doi:10.3390/molecules23040863