Salicylic acid (BHA)

Yes. BHA stands for "beta hydroxy acid", and in cosmetics the term is effectively a synonym for salicylic acid: it is the only BHA you will see on a label. If a product says "BHA 2%", it means 2% salicylic acid. What separates it from the AHAs (glycolic, lactic) is not strength but where it works: AHAs are water-soluble and act on the surface, while salicylic acid is oil-soluble, so it gets inside the pore. That is why it is the one recommended for blackheads and oily skin.

AHAs (glycolic, lactic, mandelic) are water-soluble and exfoliate the outermost layer: good for uneven texture, surface marks and dry skin. BHA (salicylic) is oil-soluble and can get through sebum, so it clears the pore from inside: good for blackheads, congested pores and oily or acne-prone skin. You do not have to pick one forever, but do avoid stacking them on the same night: they add irritation without adding results.

Yes — it's the reference active for them. Being oil-soluble, it dissolves into the pore's sebum and clears it from the inside — something no AHA can do. Blackheads take weeks to soften and clear: consistency, not force.

A gentler derivative of salicylic acid, widely used in Korea due to regulatory limits on pure BHA. 4% betaine salicylate is roughly equivalent to 2% salicylic acid, with less irritation. It's the BHA you'll find in COSRX and many other K-beauty brands.

Many oily skins tolerate it daily at 0.5–2%, especially in toner form. But if you notice tightness or flaking, cut back to 2–3 times a week: more exfoliation doesn't mean less acne, and a damaged barrier makes breakouts worse.