Glycolic Acid

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The words “acid” and “chemical peel” often conjure up horrifying images of Samantha’s botched job from Sex and the City. But in reality, acids—specifically hydroxy acids—just might be the key to the youthful, glowy skin we’re all looking for. Unlike the harsh beauty treatments of the ‘90s, these mild acids gently slough off dead skin cells to reveal a dewy, radiant complexion.

The holy grail of hydroxy acids? Glycolic acid. The super-popular, much-studied AHA (short for alpha hydroxy acid) has a reputation for delivering legit results, making it one of the best skincare ingredients you can have in your medicine cabinet.

What Is Glycolic Acid and How Does It Work? 

Usually made from sugarcane, glycolic acid is a type of AHA, a group of acids that occur naturally in foods (usually sugary fruits) and some animals. Like all hydroxy acids, glycolic acid is primarily an exfoliant, but it’s especially effective because of its size: Its tiny molecules (the smallest of all AHAs!) allow it to penetrate deep into the skin. 

To understand how glycolic acid works, it helps to know what causes dull, dry skin in the first place. Your skin has a protective top layer made up of dead skin cells (called the stratum corneum). Your body naturally sheds these dead cells to make room for the new guys, but it doesn’t always do a great job. And as you age, this shedding happens a lot less often, causing dead skin cells to build up even more.

When that top layer gets too thick, your skin starts to look lackluster. That’s where glycolic acid comes in. Whereas manual exfoliators (scrubs, loofahs, brushes) use friction to physically remove dead skin, chemical exfoliators like glycolic acid dissolve the “glue” that holds the dead skin cells together, allowing them to be easily swept away.

Glycolic Acid Benefits

By sloughing off dead skin cells, glycolic acid helps skin immediately look healthier and more radiant. It also stimulates cell turnover—in other words, it encourages the skin to produce more new cells and push the dead ones out—further improving texture and tone. This entire exfoliation process can help with tons of different skin issues, from acne (more on that below) and dark spots to keratosis pilaris and psoriasis.

Glycolic acid also prepares your skin to better absorb other skincare products, which otherwise would haven’t been able to penetrate that top layer of skin, and creates a nice, smooth base for makeup. 

But it doesn’t stop there: Because its molecules are so small, glycolic acid is able to make its way past the stratum corneum into the dermis, where it stimulates collagen production, resulting in firmer skin and fewer fine lines and wrinkles. Glycolic acid is also a humectant, which means it helps skin stay hydrated, making it smoother and plumper.

Glycolic Acid for Acne

Since one of the main causes of acne is dead skin cells clogging up pores, glycolic acid can be great for breakout-prone skin. Not only does it help bust up the gunk that results in zits and blackheads, but by speeding up cell turnover, it also keeps skin clearer and healthier.

However, for more serious acne, most experts recommend using a BHA (beta hydroxy acid) like salicylic acid, which is oil soluble (AHAs are water soluble) and therefore can penetrate deeper into sebum-clogged pores.

Who Is Glycolic Acid Good For?

Glycolic acid works for nearly every skin type, but if you have super-sensitive skin or rosacea, you may find it too irritating (some light tingling is fine, burning and peeling is not). While it’s generally pretty gentle, glycolic acid is still a powerful exfoliator, so it’s best to avoid if your skin is chapped, sunburnt, or otherwise irritated.

People with darker skin tones should also be careful about overusing high-concentration AHAs, which, in rare cases, may cause pigmentation issues.

What to Look For in Glycolic Acid Products

When shopping for glycolic acid products, there are two things you’ll want to look at: the concentration and the pH. Concentration refers to how potent the product is—that’s the percentage you usually see on the bottle.

The pH is important because glycolic acid won’t penetrate the skin if it’s too high but will cause irritation if it’s too low. Unfortunately, the exact pH often isn’t listed on the packaging, so you’ll have to do some digging or test yourself with pH strips. But some brands will say something like “low pH” or “medical-grade pH.” 

As a general guideline, seek out glycolic acid products that have a pH of less than 4 and a concentration of 4-10%. 

How to Use Glycolic Acid

Given everything glycolic acid does for your skin, it’s probably no surprise that the wonder ingredient shows up in tons of different products—cleansers, overnight creams, peels, body lotions, even foot treatments. If you’re just getting started, look for a product with a lower concentration and apply once a week to let your skin get used to it. Many derms recommend starting with a cleanser, since it washes off.

If your skin seems to tolerate glycolic acid, work up to using it two or three times a week. You can even use it daily, if that works for your skin, but note that some higher concentration products, like masks and at-home peels, should only be used once or twice a month.

Regardless of how you apply, always wear a broad-spectrum, SPF 30 (or higher) sunscreen during the day. Glycolic acid makes you more sensitive to the sun’s rays, even after you stop using it.

Next Up: Hyaluronic Acid