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.
Salicylic Acid is 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. 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. It belongs to a class of ingredients called salicylates. This structure is important because it makes salicylic acid more oil-soluble so it can penetrate into the pores of the skin.
Both alpha and beta hydroxy acids exfoliate the skin, but AHAs are water-soluble, while BHAs are oil-soluble Examples of AHAs, for reference, include glycolic and lactic acids. Generally, oil-soluble ingredients like salicylic acid penetrate through the lipid layers between the skin cells more readily. This means they can penetrate the skin at a deeper level than their water-soluble counterparts. AHAs work well on the skin's surface to loosen old, dead skin and reveal fresh newer skin.. 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 and acts as an anti-inflammatory which helps red inflamed pimples and pustules go away faster. The ingredient can penetrate so deeply into skin that actually breaks down the connections between skin cells. Once it has penetrated the skin, the acid part of the molecule can dissolve some of the intracellular 'glue' that holds skin cells together.
This breaking down of skin cells also promotes exfoliation. Salicylic acid is considered a keratolytic medication, which means that it's perfect for supreme exfoliation. Keratolytic medications cause softening and sloughing of the top layer of skin cells. Salicylic acid also loosens and breaks apart desmosomes (attachments between cells in the outer layer of skin). "This 'desmolytic' action encourages exfoliation of skin and unclogging of pores.
Bonus: Salicylic acid can help with dandruff
Salicylic acid isn't just for blackheads, according to experts. At lower levels, salicylic acid can speed up the desquamation process and aid in conditions such as dandruff and seborrheic dermatitis, which are caused by a slowing down of skin cells sloughing off.