AHA vs BHA — Which Acid Does Your Skin Actually Need?

AHAs and BHAs are both chemical exfoliants, but they work differently, target different skin concerns, and suit different skin types. Getting this wrong means either under-treating your skin or over-irritating it. Here’s the definitive breakdown.

The Core Difference

AHAs (alpha hydroxy acids) are water-soluble acids that work on the skin’s surface. They dissolve the bonds between dead skin cells, accelerating their shedding and revealing fresher skin underneath. Because they’re water-soluble, they can’t penetrate past the surface layer of skin into the pore.

BHAs (beta hydroxy acids) are oil-soluble. This single property changes everything: oil-solubility allows BHAs to penetrate into the pore lining, dissolve the oil and debris trapped inside, and exfoliate from within the follicle. BHAs also have natural anti-inflammatory properties that AHAs don’t.

AHAs: Types and What They Do

Glycolic acid is the most studied AHA and the most effective. It has the smallest molecular size of all AHAs, which means deeper penetration and faster, more dramatic results. It brightens, exfoliates, reduces fine lines, and stimulates collagen at higher concentrations. It’s also the most irritating AHA — dry and sensitive skin types should start with lower concentrations (5–7%) or choose a gentler AHA instead.

Lactic acid is the second most effective AHA and significantly gentler than glycolic. It has a larger molecular size (shallower penetration), making it better for sensitive skin and beginners. It also has unique humectant properties — it draws moisture into the skin while exfoliating, which makes it the best AHA for dry skin. The Ordinary Lactic Acid 10% + HA is one of the most popular entry points for chemical exfoliation.

Mandelic acid has the largest molecular size of the common AHAs, meaning the mildest effect. It’s particularly effective for hyperpigmentation on darker skin tones because its gentleness reduces the risk of post-inflammatory hyperpigmentation that aggressive exfoliation can trigger. Good for sensitive skin that can’t tolerate even lactic acid.

BHAs: What You Need to Know

The only widely used BHA in skincare is salicylic acid. It’s derived from willow bark and is genuinely unique in its ability to penetrate and exfoliate inside the pore. This makes it the definitive ingredient for blackheads, whiteheads, congestion, and acne. It also reduces sebum production and has anti-inflammatory and mild antibacterial properties. Effective concentrations are 0.5–2% — you don’t need more than 2%. Paula’s Choice 2% BHA Liquid Exfoliant is the benchmark product and has been independently tested more than almost any other skincare product on the market.

There is a second BHA — beta-lipohydroxy acid (LHA) — used by La Roche-Posay in some products. It’s a derivative of salicylic acid with even gentler exfoliation. Worth considering if salicylic acid causes dryness but you still need pore-focused exfoliation.

AHA vs BHA by Skin Concern

Blackheads and congested pores: BHA (salicylic acid) is the clear winner. AHAs cannot penetrate into pores and will not significantly address blackheads. If clogged pores are your primary concern, salicylic acid is the only chemical exfoliant that directly targets the cause.

Active acne: BHA wins. Its pore-penetrating ability, anti-inflammatory properties, and mild antibacterial effect make it far more effective for acne than AHAs. AHAs can help with post-acne marks but don’t treat active breakouts.

Dull skin and uneven texture: AHAs win. Surface-level exfoliation is exactly what AHAs do best. A consistent AHA routine visibly smooths skin texture and improves radiance faster than BHA for non-acne-related concerns.

Hyperpigmentation and dark spots: AHAs win. Glycolic and lactic acid accelerate cell turnover and bring pigmented cells to the surface faster, fading dark spots more efficiently. Mandelic acid is particularly good for darker skin tones.

Fine lines and anti-ageing: AHAs win, particularly glycolic acid at 8–10%+. Long-term glycolic acid use has been shown to stimulate collagen production. BHAs have minimal direct anti-ageing effect beyond general exfoliation.

Dry skin: Lactic acid (AHA) wins. It exfoliates while simultaneously adding moisture. Salicylic acid can be too drying for already-dry skin.

Oily and combination skin: BHA (salicylic acid) wins. Oil-solubility means it works with your skin’s excess oil rather than fighting it. It reduces sebum and keeps pores clear — the two biggest concerns for oily skin.

Can You Use Both Together?

Yes, but with care. The most common approach is to alternate — AHA one evening, BHA the next. Or use a product that combines both (like Paula’s Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel, used once weekly). Using both in the same routine on the same night can cause over-exfoliation, especially for dry or sensitive skin. If you have oily skin and your skin has adapted to regular exfoliant use, using both on the same night is possible but not necessary.

The Bottom Line

If you have oily, acne-prone, or congested skin — start with BHA (salicylic acid). If you have dry, dull, or ageing skin — start with AHA (lactic acid for sensitivity, glycolic for maximum effect). If you have combination skin with both congestion and texture concerns, alternating both is often the most effective approach. The one rule that applies regardless: introduce one at a time, start with low concentrations, and always wear SPF — chemical exfoliants increase photosensitivity without exception.

Prices checked March 2026. Patch test new products before full application. Affiliate Disclosure: TrueDailyGlow participates in affiliate programmes. We may earn a small commission on qualifying purchases at no extra cost to you.