Chemical exfoliants confuse people because so many share the label "acid" while behaving quite differently. Two of the most common — salicylic and glycolic acid — are often presented as interchangeable, but they work in different parts of the skin and suit different concerns. Picking the right one matters more than picking the trendiest.
The key difference comes down to whether an acid prefers oil or water.
Glycolic: the surface resurfacer
Glycolic acid is water-loving and works mainly on the surface, loosening the bonds between dead skin cells so they shed more evenly. This can leave skin smoother and brighter, and over time help with rough texture and dullness. Because it works on the top layer broadly, it is popular for general radiance and uneven tone.
Its strength is also its risk: on sensitive or dry skin, or used too often, it can over-exfoliate and irritate. Less is usually more.
Salicylic: into the pore
Salicylic acid is oil-loving, which lets it penetrate into oily, clogged pores and help clear them from within. That makes it particularly suited to oily and acne-prone skin, blackheads and congestion, where a surface exfoliant cannot reach. It also has mild calming properties.
If your main concern is breakouts and blocked pores rather than overall texture, salicylic is usually the more logical choice.
Choosing and using safely
A rough guide: reach for salicylic for oily, congested, breakout-prone skin, and glycolic for texture, dullness and uneven tone on skin that can tolerate it. You rarely need both at full strength, and stacking exfoliants is a fast route to a damaged barrier.
Start once or twice a week, never combine strong exfoliation with other harsh actives at once, and always wear sunscreen, since exfoliated skin is more vulnerable to the sun. If skin turns tight or stingy, that is a cue to slow down.