If you’re a beauty enthusiast, I assume you already know the basics of alpha-hydroxy acids (AHAs) in skincare. They’re everywhere! But as part of our mission to educate, we like to go beyond what’s common knowledge and reveal some lesser-known facts about a given ingredient while polishing up our existing knowledge.
I mean, knowing AHAs exfoliate the skin is one thing. But knowing how on earth an acid would trigger cell renewal is another story. Here you’ll find everything you need to know about alpha-hydroxy acids in skincare, how they work, their benefits, and so much more. Dig in!
What Are Alpha-Hydroxy Acids?
A subcategory of hydroxy acids, alpha-hydroxy acids is a group of acids used in skincare products like serums, toners, and cleansers to exfoliate the skin (1).
They’re sometimes called fruit acids as well. They can both be derived from natural sources and produced synthetically.
Besides skincare, alpha-hydroxy acids are also used in professional skin treatments like chemical peels. AHAs help with a variety of skin concerns like acne, hyperpigmentation, scars, wrinkles, sun damage, and rough skin (2).
The list of alpha-hydroxy acids is as follows (1):
- Glycolic acid, usually derived from sugar cane
- Lactic acid, usually derived from milk
- Citric acid, usually derived from citrus fruits like lemons
- Tartaric acid, usually derived from grapes
- Malic acid, usually derived from apples
- Mandelic acid, usually derived from almonds
How Do These Acids Differ?
All of these acids are unique. They differ in the way they work on the skin because of their molecular structure. Here’s the list of the molecular weight of each alpha-hydroxy acid.
- Glycolic Acid: 76.05 g/mol
- Lactic Acid: 90.08 g/mol
- Malic Acid: 134.09 g/mol
- Tartaric Acid: 150.09 g/mol
- Mandelic Acid: 152.15 g/mol
- Citric Acid: 192.12 g/mol
So what does this mean? It means that glycolic acid would be the most penetrative whereas citric acid would be the least. That’s why glycolic acid is so common in our skincare products.
But there’s a catch. Because it’s the most penetrative of the bunch, it’s also the one that carries the most risk for irritation. More on this under the side effects section.
Acids that are high in molecular weight, the ones that are less penetrating, are usually combined with each other to achieve cumulative results.
That’s why you don’t see a lot of citric acid serums but you see lactic acid serums that are enriched with citric acid.
How Do Alpha-Hydroxy Acids Work?
The dead skin cells on the top layer of your skin are linked to each other. And alpha-hydroxy acids dissolve these links (bonds) that hold those cells together (2).
It means that AHAs prompt exfoliation, which means they slough off dead skin cells. This is why hydroxy acids are also called chemical exfoliants.
By exfoliating the skin, AHAs give you smoother skin while diminishing other concerns such as acne and wrinkles in the process.
What Are The Benefits of Alpha-Hydroxy Acids For Skin?
There are numerous benefits of alpha-hydroxy acids for the skin. AHAs target two main skin concerns, acne, and wrinkles, with one major property, exfoliation. Here’s how AHAs help your skin in more detail.
1. They exfoliate.
AHAs are primarily exfoliants (3). All other benefits listed below are the result of this property.
Your skin gets rid of dead skin cells as part of its natural cell turnover cycle. This is an internal process. New cells are born beneath and replace older cells above.
But as we age, it takes longer for our skin to complete this cycle and renew itself. And our skin looks dull, feels rough, and shows more impurities.
That’s where chemical exfoliants like AHAs come in. AHAs stimulate cell turnover from the outside (external) by exfoliating the skin. With the removal of old cells, AHAs give you a smoother and softer complexion.
I came across a phrase I really liked while doing research for this article. Maybe it was because that was the only phrase I could understand because of the heavily scientific jargon of the article. But it summarizes the whole thing.
“Perhaps the greatest irony in biology is that life depends on death -programmed cell death, that is” (4).
2. They stimulate collagen production.
Because they’re exfoliants, AHAs are incredibly anti-aging. AHAs stimulate collagen production (5). It’s the protein that gives you youthful skin.
As we age, we produce it less. Not to mention our bad habits and daily UV exposure that damage our healthy collagen.
By stimulating collagen synthesis, AHAs improve skin elasticity and give your firmer, and healthier skin.
3. They help with discolorations.
Dark spots, either from acne or sun damage, can be difficult to deal with. But with regular exfoliation and with the constant renewal of the top layer of your skin, AHAs reveal a more even skin tone. They also brighten the skin and help achieve a radiant complexion.
4. They help with acne.
AHAs also help with congested skin and blackheads because of the way they get rid of stubborn skin flakes. When those dead skin flakes stay on the skin too long, they’re more likely to settle inside the pores and clog them.
By removing them with exfoliants like AHAs, you prevent your pores from getting clogged and congested, which is what makes the skin prone to acne in the first place.
5. Each AHA offers a unique benefit.
We’ve mentioned that each AHA is unique because of its molecular weight. But that’s not it. For example, lactic acid has additional benefits of boosting hydration on the skin, which results in plumper skin. This acid is great for people with dry, dehydrated skin.
Additionally, citric, tartaric, and malic acids, besides being exfoliants, are also antioxidants (6). They help treat and prevent free radical damage on the skin.
6. They make the skin more permeable.
Exfoliation is like deep-cleanse. You remove the barrier that’s preventing your skincare products from penetrating the skin.
That’s why exfoliation is one of the best ways to increase the benefits of your skincare products. Your skincare products absorb better and work better.
Alpha-Hydroxy Acids vs Other Hydroxy Acids
Think of these acids as a big family under the name “hydroxy acids”. Besides the sub-group alpha-hydroxy acids, we have beta hydroxy acids and polyhydroxy acids.
Beta hydroxy acids include mainly salicylic acid whereas polyhydroxy acids include lactobionic acid, gluconolactone, and maltobionic acid.
In the grand scheme of things, AHAs are the best at exfoliating the skin. They differ from BHAs, which are oil-soluble and work best for oily skin.
PHAs are the gentlest exfoliants with additional hydrating and antioxidant benefits. But when pure, unadulterated exfoliation is concerned, AHAs, especially glycolic acid, are the absolute best.
What Are The Side Effects of AHAs For Skin?
Because of the way they penetrate the skin, alpha hydroxy acids can induce irritation on the skin and cause stinging and burning. However, this does not apply to all.
As I mentioned above, glycolic acid is the one that can be considered riskier for people with sensitive skin because of its molecular weight.
But this side effect can easily be mitigated simply by using a low concentration glycolic acid product. Similarly, you can choose an AHA like tartaric acid, which is very unlikely to irritate.
Another common side effect of alpha-hydroxy acids is photosensitivity. When you exfoliate with acids, your skin becomes more sensitive to sunlight and more prone to sunburn. Again, this can be prevented simply by wearing SPF regularly.
Can You Use AHAs With Other Actives?
Exfoliating acids do not go well with other active ingredients. They don’t even go well with each other unless they’re in one single product.
For example, do not use a glycolic acid cream over a glycolic or lactic acid serum. The combination will result in a much higher concentration of the acids, which will probably irritate your skin and cause inflammation.
Additionally, avoid using AHAs with other hydroxy acids like beta hydroxy acids. And avoid using vitamin C or retinol in the same routine you use AHAs. When in doubt, stick with one active ingredient.
What Can You Use With AHAs?
Some ingredients go perfectly well with AHAs even if you use them in the same routine. These are harmless on their own and harmless with others.
You can use hyaluronic acid, which is a humectant that hydrates the skin. You can use ceramides in the form of a moisturizer, which will moisturize the skin. Basically, anything hydrating, moisturizing, or soothing will be OK to mix with AHAs.
How To Use Alpha-Hydroxy Acids?
Well, knowing what AHAs are and how they work is the first step if you want to get the most out of them. Now that you’ve got that covered, here’s how you can use AHAs and how you can incorporate them into your skincare routine.
First of all, take another look at the molecular weights of the acids and decide which one to go for. AHAs come in serums, exfoliating toners, peel pads, and even cleansers.
For daily use, cleansers, toners, and pads are great. At-home peels and treatments tend to be more concentrated and should be used once or twice a week.
But as a general rule of thumb, it’s always in your skin’s best interest to start slow with active ingredients. No matter which acid or product you use, start slow and let your skin adjust to it.
AHAs are great for normal, combination, oily, and acne-prone skin types. Because these skin types tend to be more tolerant towards actives.
But people with very dry and sensitive skin and people with rosacea are not the best candidates for AHA products.
For best results, use your AHA products on dry, clean skin. They’ll be more penetrating and effective. Then follow with your serums and moisturizers.
The Best Products With Alpha-Hydroxy Acids
If you’re ready, below are some of the best products made with alpha-hydroxy acids. From serums to toners, and from glycolic acid to mandelic acid, there is plenty.
Lucky for us, there is a ton of budget-friendly products made with alpha-hydroxy acids. And The Ordinary offers one of the most effective ones. This is a daily exfoliating glycolic acid toner made with a concentration of 7%. It gets rid of dead skin cells, prevents congestion, brightens the skin, and is great for both acne and wrinkles. A rich blend of amino acids boosts hydration while aloe calms the skin. It’s non-comedogenic and fragrance-free.
Another affordable option is this lactic acid serum. It’s minimal yet super effective in smoothing out the skin texture through exfoliation. 10% lactic acid eliminates flakiness while increasing hydration. To amplify hydration, the serum packs 1% hyaluronic acid to bind water to the skin, plump it up, and reduce the visibility of lines and wrinkles.
This is a glycolic acid face cream perfect for people who deal with stubborn dry patches. The exfoliating moisturizer dissolves dead skin cells but doesn’t dry out your skin. The 10% concentration of AHAs includes both glycolic and citric acids and they’re delivered through a softening base made with shea butter. The added citric acid provides antioxidant benefits as well. The moisturizer stimulates cell turnover, improves skin textures, and helps with sun damage.
These AHA peel pads are incredible for any skin type looking to increase radiance and reduce dullness. The concentration is 20% glycolic acid, which is pretty packed. The pads are also soaked in soothing aloe water, replenishing rose water, and brightening licorice. Swipe one over in the PM after you clean your face to achieve smoother, brighter, and tighter skin.
This is a night cream with a gel texture made especially for oily skin types. It’s great for acne-prone skin types that are dealing with dehydration. It’s made with mandelic acid to decongest the skin and reduce acne. Plus, it has another hydroxy acid; polyhydroxy acid. As a PHA, gluconolactone is incredibly gentle on the skin and is majorly hydrating. The oil-free cream is perfect for exfoliating and moisturizing oily skin without clogging pores.
This exfoliator utilizes a blend of AHAs for the ultimate skin renewal. It has glycolic, lactic, malic, and tartaric acids to resurface the skin, plump it up, eliminate roughness, and boost radiance while offering antioxidant benefits. The concentration is a total of 10%. The formula also has soothing oatmeal and allantoin as well as hydrating hyaluronic acid, cucumber, and ceramides. Use it to soften wrinkles, fade dark spots, and clear up blemishes.
AHAs make the best ingredients in a face mask. This exfoliating mask utilizes malic, mandelic, tartaric, and lactic acids to rejuvenate the skin. It also has salicylic acid from the beta hydroxy acids family to better target pores and acne. And it has enzymes, which are also natural exfoliators that work super gently on the skin. Use it as part of your at-home facial.
So this is what alpha-hydroxy acids are, how they work, what they do, and some products to find them in. Even though all of these 6 acids are alpha-hydroxy acids, they’re usually marketed with their own names. So instead of looking for an alpha-hydroxy acid product, it’s best to shop for the exact acid in whatever form you prefer like a toner or serum. Now that you know what each one does, hopefully, your search should take a lot less.
Read Next: The Best Glycolic Acid Serums
- Tang, S. C., & Yang, J. H. (2018). Dual Effects of Alpha-Hydroxy Acids on the Skin. Molecules (Basel, Switzerland), 23(4), 863. https://doi.org/10.3390/molecules23040863
- Moghimipour E. (2012). Hydroxy Acids, the Most Widely Used Anti-aging Agents. Jundishapur journal of natural pharmaceutical products, 7(1), 9–10.
- Kornhauser, A., Coelho, S. G., & Hearing, V. J. (2010). Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clinical, cosmetic and investigational dermatology, 3, 135–142. https://doi.org/10.2147/CCID.S9042
- Raj, D., Brash, D. E., & Grossman, D. (2006). Keratinocyte apoptosis in epidermal development and disease. The Journal of investigative dermatology, 126(2), 243–257. https://doi.org/10.1038/sj.jid.5700008
- Baran, R., & Maibach, H. (2017). 6. Organic acids with novel functions: Hydroxy, bionic, n-acetylamino acids and n-acylpeptide derivatives [E-book]. In Textbook of Cosmetic Dermatology (Series in Cosmetic and Laser Therapy) (5th ed., pp. 56–70). CRC Press. https://doi.org/10.1201/9781315160504
- Draelos, Z. D. (2011). Chapter 40: Clinical uses of hydroxy acids [E-book]. In Cosmetic Dermatology: Products and Procedures (pp. 327–334). Wiley-Blackwell. https://doi.org/10.1002/9781444317657