AHA and BHA are on half the products in the skincare aisle, and the labels rarely explain what the letters mean.
Glycolic acid is the most common AHA. Salicylic acid is the only BHA you will meet. Both are exfoliants — they loosen dead skin cells — but they work in different places, and that determines what each one is good for.
One chemical property explains the whole difference: glycolic acid mixes with water, salicylic acid mixes with oil.
The split here is unusually clean, and it comes down to solubility. Salicylic acid takes the pore row because it dissolves in oil and can travel into a clogged follicle. Glycolic acid takes the pigment row because it clears stained surface cells efficiently, and it reaches a little into the dermis at higher strengths. Both cost you something on the barrier row — that is what exfoliation is.
Blackheads and clogged pores | Salicylic acid | Moderate
The pore is full of oil. Only the oil-soluble acid can get in there. Glycolic acid works across the top and stops.
Dullness and rough texture | Glycolic acid | Strong
It lifts dead surface cells efficiently, which is what produces the immediate glow people notice.
Sun damage and uneven tone | Glycolic acid | Moderate
It speeds off pigmented surface cells, and at higher strengths it offers some collagen support. Salicylic acid does little here.
Oily skin | Salicylic acid | Moderate
It suits oily skin chemically and reduces the congestion oil creates.
Dry or mature skin | Glycolic acid | Moderate
It is the more hydrating of the two — glycolic acid attracts water — and better matched to texture and tone concerns.
Redness and sensitivity | Salicylic acid | Moderate
It is anti-inflammatory, being in the aspirin family. Glycolic acid is the more likely of the two to sting.
Body use — keratosis pilaris, back acne | Depends | Moderate
Glycolic or lactic acid for the rough bumps on arms and thighs. Salicylic for back and chest breakouts.
Skin of color | Salicylic acid, usually | Moderate
Both are usable, but glycolic acid at higher strengths is more irritating, and irritation is what leaves dark marks. If you use glycolic, start at 5–7% rather than 10% and build slowly.
Sun sensitivity | Salicylic acid | Consensus
Glycolic acid increases sun sensitivity more noticeably. Both call for daily sunscreen; glycolic makes it non-negotiable.
You can use both, but not on the same night, and most people do not need to.
Two exfoliating acids stacked together is the fastest route to a stripped, stinging barrier — and a damaged barrier makes every problem worse, including the ones you were trying to fix.
If you want both:
- Alternate nights, or use salicylic in the morning and glycolic twice a week at night.
- Never on a night you use a retinoid.
Pick just one if: clogged pores and oiliness → salicylic acid. Dullness, rough texture, and uneven tone → glycolic acid.
Two or three times a week is usually plenty for either. Daily acid use is rarely necessary and frequently counterproductive.
Sunscreen is part of the treatment, not an afterthought. Both acids thin the layer of dead cells that offers a small amount of natural protection.