Chemical exfoliants are among the most effective actives in skincare — but choosing between AHA and BHA confuses a lot of people. Both dissolve dead skin cells, but they do so through different mechanisms and reach different skin layers. Here's exactly how to choose.
AHA — Alpha Hydroxy Acid
AHAs are water-soluble acids derived mostly from natural sources. The most common are glycolic acid (from sugarcane), lactic acid (from milk), mandelic acid (from almonds), and malic acid. They work on the skin's surface by breaking the bonds between dead skin cells, encouraging them to shed more evenly. Result: smoother texture, brighter tone, reduced fine lines. Because AHAs are water-soluble, they don't penetrate into pores.
BHA — Beta Hydroxy Acid
The main BHA used in skincare is salicylic acid. It's oil-soluble — meaning it can penetrate through sebum and deep into pores. This makes it uniquely effective for blackheads, whiteheads, and acne. BHA also has anti-inflammatory properties, which is why it's a go-to for acne-prone and reactive skin. Capryloyl salicylic acid (LHA) is a gentler, slower-releasing derivative.
Key Differences
- AHA: water-soluble, works on surface; BHA: oil-soluble, penetrates pores
- AHA: better for dry, dull, or aging skin; BHA: better for oily, acne-prone skin
- AHA: more effective for hyperpigmentation and texture; BHA: more effective for blackheads and breakouts
- AHA: increases sun sensitivity (always use SPF); BHA: also photosensitizing but slightly less so
- AHA: typically higher irritation potential at equal efficacy; BHA: anti-inflammatory properties buffer irritation
Which Should You Use?
Dry or mature skin with texture or pigmentation concerns → AHA (lactic acid is gentlest, glycolic is most potent). Oily, acne-prone, or clogged-pore skin → BHA (salicylic acid 0.5–2%). Combination skin → you can use both, but on different days. Sensitive skin → start with lactic acid (AHA) at low concentration, or mandelic acid which has a larger molecule and penetrates more slowly.
Can You Use Both?
Yes — many products combine AHA and BHA. If using separately, don't layer them in the same routine (double exfoliation increases irritation risk). Alternate days or use one in the morning and one at night. Always follow with moisturizer and SPF in the morning.
Common Mistakes
Over-exfoliating is the most common mistake — it strips the barrier and causes more problems than it solves. Start at 1–2 times per week and build up. Never apply to broken or actively irritated skin. Always wear SPF the next morning. Don't combine with high-concentration retinol in the same routine until your skin is accustomed to both.