Do your eyes cross when reading beauty product labels? I’m going to be honest here and say that I used to call it quits after the first 10-syllable ingredient I’d encounter. But a little while ago, I determined to figure this stuff out because it was time I knew what the heck that 32-character-long vaguely Latin-looking word was doing to my face.

Once you know what the various acids do, I swear, it will demystify 93 percent of products that you are considering for your skincare routine. You’ll know exactly what you’re looking for, and whether what’s listed on that moisturizer or serum is going to live up to the clever marketing and great packaging that it comes in.

Here are 9 acids that are frequently found in beauty products and what you should know about them.


In the alpha hydroxy acid (AHA) category, citric acids have been studied for their ability to exfoliate and are a top pick for aging skin types. AHAs, as a refresher, are a category of acids that promote collagen formation and even out skin tone. One caution about citric acids: they can cause a slight stinging sensation, so if you have sensitive skin, you might want to consider a different AHA.   


This acid belongs in the polyhydroxy acid (PHA) category. Because PHAs have a larger molecule size, they penetrate your skin layer at a slower rate, which makes PHA acids great for sensitive skin. Aside from gluconolactone being a PHA, it also bolsters your skin barrier, which results in skin-firming benefits. Additionally, it protects against UV damage. Gluconolactone is a great ingredient to see on the back of a serum or moisturizer if you have sensitive or dehydrated skin. 


One of the most studied acids out there, glycolic acid is extracted from sugar cane and belongs in the AHA category. This hard-working acid acts as an exfoliant, removing old skin cells and minimizing the appearance of aging or discolored skin. You’ll often find it in acne treatments to help with dark spot control.


Hyaluronic acid is a heavyweight in the acid world. It’s likely you have at least a nodding acquaintance with this one, but for those starting from zero… Hyaluronic acid benefits skin through its moisture-carrying capacity. This is why so many moisturizing products have hyaluronic acid as an ingredient because it boosts your skin’s ability to hold on to hydration—and properly hydrated skin looks firmer, smoother, and younger.


This acid in the AHA category can be extracted from milk, but more often than not cosmetic companies use a lab-synthesized form of lactic acid because it’s easier to work with. Depending on the concentration of lactic acid in the product, it can work as an exfoliator. In lower concentrations, it has moisturizing benefits and can help to reduce redness and smooth skin tone.


Lactobionic acid is often confused with lactic acid, but lacticacid is an AHA; lactobionicacid is a PHA. Remember that PHAs have a larger molecular structure than AHAs? So, the absorption rate of lactobionic acid is slower than that of lactic acid, thus limiting how deeply it penetrates your skin barrier. Dermatologists believe that this limitation reduces side effects common to sensitive skin types.


Mandelic acid has exfoliating properties, but because its molecular size is twice as big glycolic acid, it penetrates the skin at a slower speed. A good choice for sensitive skin types who are looking for an alternative to glycolic acid-based products. Mandelic acid products are a light-sensitive acid, so it needs to be sold in an opaque container. Anything else, and you’re being hoodwinked.


Salicylic acid is a beta hydroxy acid that gets to the root of a variety of common acne issues. It dives far into pores and does a deep clean all the way down, as well as to the surface area, eradicating the acne bacteria that is causing your breakout. Also, added bonus, salicylic acid soothes, hydrates, and can even skin tone out. A real superstar in the acid world.


Tartaric acid (one of the main acids in wine!) belongs in the alpha hydroxy acid category and with all the benefits that AHAs have. Primarily, tartaric acid is added to ingredients to serve as an antioxidant. What does this mean for your skin? Antioxidants limit the ability of certain molecules that would otherwise weaken your skin’s elasticity and cause discoloration. So, yeah, antioxidants protect against the effects of life (kinda like your Happy Hour wine, but for your face).

—Tomoko Matsuoka


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