Glycolic Acid

Glycolic acid is one of those ingredients that falls into the "oldie but goodie" category of skincare superstars. While it's by no means the newest or trendiest ingredient out there—it's been used in dermatology for over three decades—it is a tried-and-true staple, favored by dermatologists for its long list of proven benefits. And, surprisingly, those benefits aren't limited to exfoliation.

GLYCOLIC ACID

TYPE OF INGREDIENT: Alpha-hydroxy acid

MAIN BENEFITS: Acts as a chemical exfoliant by loosening the bonds between dead skin cells while helping to treat acne. Glycolic acid also stimulates collagen production and acts as a humectant, attracting moisture to the skin.

WHO SHOULD USE IT: Glycolic acid is well-tolerated by most skin types and is gentle enough that usually, even those with sensitive skin can use it, says Howe.

HOW OFTEN CAN YOU USE IT: This depends largely on your skin and the particular product you're using, but in certain situations, it can be used daily.

WORKS WELL WITH: Other humectants, such as hyaluronic acid, though it's also often combined with lightening ingredients such as kojic acid or hydroquinone.

DON'T USE WITH: Be especially cautious when pairing it with other acids and retinoids, cautions Mariwalla.

What Is Glycolic Acid?

"Glycolic acid is an alpha-hydroxy acid derived from sugarcane," explains Howe. Because it comes in various strengths, it has various applications, ranging from over-the-counter, leave-on creams to medical-grade, chemical peels that only dermatologists should apply, adds Mariwalla. Looking at the big picture of all of the different types of acids out there, it falls on the gentler end of the spectrum, which is what makes it a good option for almost anyone. However, as far as AHAs specifically go, it's one of the stronger, more potent ones; because it has the smallest molecular weight of any alpha-hydroxy acid, it penetrates the skin more easily, explains Howe. 

In other words, it's more effective than other common AHAs such as lactic acid or malic acid, though subsequently not quite as gentle.

Benefits of Glycolic Acid for Skin

Essentially every acid acts as a chemical exfoliant, but glycolic acid has several other notable attributes.

• Removes dead skin cells to reveal softer, smoother skin: Glycolic acid works by loosening the binding between dead skin cells, allowing them to slough off, says Mariwalla. (If you want to get technical, the term for this is desquamation.)
• Is an effective acne-fighter: By encouraging the shedding or peeling of cells on the skin's surface and those lining the pores, glycolic acid prevents the formation of clogged pores—the main factor that contributes to acne, says Howe.
• Works deeper in the skin to stimulate collagen production: Glycolic acid's effects aren't limited to the skin's surface. It's also been found to work on the skin's deeper layers to promote collagen synthesis, which is why it's considered a good anti-aging ingredient, Howe says. (Mariwalla notes, however, that unlike its exfoliating effects, the youth-boosting benefits come with continued use over time. In other words, while you'll see smoother, more even skin pretty much instantly, it'll take time to notice an improvement in lines and wrinkles.)

Side Effects of Glycolic Acid

At the end of the day, an acid is an acid. And that means that there's always going to be the potential for some redness, irritation, and peeling, particularly if your skin is sensitive to start. (Howe says that those who are eczema-prone or have a dehydrated complexion are especially at risk.)

How to Use It

Not all glycolic acid products are created equal, so your best bet is always to follow the directions for the particular product you're using. Some rely on glycolic acid alone, though many pair it with other acids specially formulated to not irritate. It's also worth noting that, even if a product specifies a concentration of glycolic acid (most OTC options contain less than 15%), this figure isn't a true indicator of how strong or effective it will be, says Mariwalla. "That's determined by the free acid value, which has to do with both the amount of glycolic acid and the pH of the product, and often times isn't listed," she says. 

If you want to err on the side of caution, stick with products that contain less, but keep in mind, it's best to start using glycolic acid gradually and build up frequency as your skin adapts. Reserving application for your nighttime routine is also a good approach since it may make your skin more sensitive, Mariwalla adds.

One of the most popular face acids, glycolic acid is an alpha hydroxy acid (AHA) that is more effective at a lower pH (usually pH 3–4). A word of caution with this beloved ingredient though: too much can be irritating and damage your skin barrier.

If you’re going to hop on this gly-train, do it slowly, starting at once per week before building up. And stick to the rule of absolutely wearing SPF in the day as this acid increases sun sensitivity.

Your skin is gonna love this: As a chemical exfoliant, it loosens the upper layers of dead skin cells so that they slough off more easily to reveal smoother, clearer skin. These results make it fantastic for treating aging skin. It can also:

• clear clogged pores
• improve skin texture and wrinkles
• fade patches of hyperpigmentation
• increase collagen production

Where to find it: Glycolic acid is usually found in leave-on exfoliants and toners, which you apply on skin after cleansing and before serums and moisturizers. If those products are too harsh, consider looking for a cleanser.