Salicylic Acid

why we use salicylic acid

The Basics

Salicylic acid is an exfoliating acid that dissolves in oil, so it works inside the pore as well as on the surface. It loosens the junctions that hold dead skin cells together, so they shed instead of building up and plugging the follicle. It's also related to aspirin and has some anti-inflammatory activity, reported to be strongest between 0.5% and 5%.¹ Expect clearer pores, fewer blackheads and smoother texture.

How does salicylic acid exfoliate?

It was long described as keratolytic, meaning it breaks down keratin. It's now recognised as desmolytic. Salicylic acid pulls apart desmogleins, the proteins inside desmosomes (the cellular rivets that hold skin cells together), so dead cells lose their grip and shed.¹

Is salicylic acid a BHA?

It's sold as a beta hydroxy acid (BHA), but the label is technically wrong. In salicylic acid, both the hydroxyl group and the acid group sit directly on a benzene ring.² The label may have come from marketing, when BHA peels launched while alpha hydroxy acids (AHAs) were popular.¹

Salicylic acid vs glycolic acid

Glycolic acid, an AHA, dissolves in water. Salicylic acid dissolves in oil, so it mixes with the skin's own lipids and the sebum inside hair follicles.¹ That's what makes it useful for oily skin.²

Does salicylic acid work on acne?

In a randomised trial of 500 people with mild to moderate acne, a 2% salicylic acid gel used once a day matched adapalene gel, a retinoid. After 12 weeks, 51% of the salicylic acid group and 43% of the adapalene group were markedly improved or clear, a difference that wasn't statistically significant.³

How strong can salicylic acid be?

In the EU, most leave-on cosmetics can carry up to 2%, rinse-off hair products up to 3%, and it can't be used in products for children under 3.⁴ In the US, acne products sold over the counter use 0.5 to 2%.⁵ Peels done in a clinic go far higher.¹

Does salicylic acid cause purging?

Purging hasn't been defined or studied in the clinical research on salicylic acid.

Can you use salicylic acid while pregnant?

On normal skin, absorption of salicylic acid at up to 25% was undetectable, though it depends on the formula, pH, strength and how much is applied. Because so little is absorbed, topical use is considered unlikely to pose a risk to a developing baby. No studies have looked at topical use in pregnancy directly, and absorption can be higher on damaged skin.⁶ Check with your doctor or midwife before starting any new active.

Salicylic acid for the scalp

On the scalp it lifts flakes, and it's usually paired with an antifungal. In a 20-person study, a salicylic acid and piroctone olamine gel and cleanser cut the average dandruff score from 2.45 to 1.10 in 4 weeks.⁷ The scalp trials combine it with an antifungal, so its own share of the result isn't known.