Here’s Exactly What Salicylic Acid Does to Your Skin

model looking in the mirror at her skin

In the over-the-counter battle against breakouts, there are a few key players you should know about, and salicylic acid is at the top of that list. Simply speaking, salicylic acid is one of acne’s biggest enemies. You reach for a product within the second you see a zit invading your face. You slather it on a pimple overnight and oftentimes, you wake up in the morning with a pimple that is dried up and much less noticeable. But, what exactly does salicylic acid do, and what are the best ways to reap its benefits? To find out, we consulted dermatologists to help break down exactly how salicylic acid works on the skin, who should (and shouldn’t) use it, and why it’s such a popular choice for staving off breakouts.

What is salicylic acid?

First off, let’s establish what salicylic acid is. It’s a little complicated, but the exact structure of salicylic acid is important in explaining why (and how) it works so well. When it comes to skin-care products, there are two classes of acids you’ll see often: beta hydroxy acids (BHAs) and alpha hydroxy acids (AHAs).

“Salicylic acid is a beta hydroxy acid,” says cosmetic chemist Randy Schueller. “[This] means the hydroxy part of the molecule is separated from the acid part by two carbon atoms, as opposed to an alpha hydroxy acid where they’re separated by one carbon atom.”

Furthermore, salicylic acid is actually derived from willow bark, says cosmetic chemist Ron Robinson, and it belongs to a class of ingredients called salicylates. Are you still with us? Good, because this is where it gets fun. “This structure is important because it makes salicylic acid more oil-soluble so it can penetrate into the pores of the skin,” Schueller says.

Both alpha and beta hydroxy acids exfoliate the skin, but AHAs are water-soluble, while BHAs are oil-soluble, explains New York City-based board-certified dermatologist Sejal Shah. Examples of AHAs, for reference, include glycolic and lactic acids.

“Generally, oil-soluble ingredients penetrate through the lipid layers between the skin cells more readily,” Shah explains. In other words, oil-soluble ingredients can penetrate the skin at a deeper level than their water-soluble counterparts.

Robinson sums up their differences succinctly. “AHAs work well on the skin’s surface to loosen old, dead skin and reveal fresh newer skin,” he says. “Salicylic acid works deeper [and is] able to penetrate into the pores to unclog them.”

What does salicylic acid do for the skin?

What all of this means is that salicylic acid can get deep into your skin to do its job. This quality is precisely what makes salicylic acid such a potent ingredient for targeting acne — especially for blackheads and whiteheads.

Once it penetrates the skin, salicylic acid “dissolves skin debris that clogs pores, [acts] as an anti-inflammatory and also helps red inflamed pimples and pustules go away faster,” explains Naissan O. Wesley, a board-certified dermatologist in Los Angeles.

The ingredient can penetrate so deeply into skin that actually breaks down the connections between skin cells, according to Schueller and Wesley. “Once it has penetrated the skin, the acid part of the molecule can dissolve some of the intracellular ‘glue’ that holds skin cells together,” says Schueller.