AHA vs. BHA: Which Chemical Exfoliant Do You Need?

Physical scrubs (walnut shells, sugar) can tear at skin microscopically. Chemical exfoliants dissolve the bonds between dead skin cells instead. Used correctly, chemical exfoliants are generally more effective, more controlled, and less damaging.

AHAs and BHAs are the two main categories. They're not interchangeable.

AHA (Alpha-Hydroxy Acid): Water-Soluble

Common types: Glycolic acid (from sugarcane), lactic acid (from milk), mandelic acid (from almonds), citric acid.

How it works: AHAs dissolve the bonds between dead skin cells at the surface. Being water-soluble, they work primarily at the skin surface [2].

Best for:

• Dry, rough, or dull skin
• Hyperpigmentation and sun spots
• Fine lines and uneven texture
• Keratosis pilaris
• Normal skin seeking improved radiance

Most common in Korean skincare: Lactic acid (gentler), glycolic acid (most studied), PHA (polyhydroxy acid — gentlest, good for sensitive skin).

BHA (Beta-Hydroxy Acid): Oil-Soluble

Primary type: Salicylic acid.

How it works: BHA is oil-soluble, so it can penetrate the sebum-filled pore lining. This makes it uniquely effective at clearing congestion inside the pore rather than just at the surface [1].

Best for:

• Oily and acne-prone skin
• Blackheads and whiteheads
• Enlarged pores
• Skin prone to fungal acne (pityrosporum folliculitis)

Side-by-Side

Factor	AHA	BHA (Salicylic Acid)
Solubility	Water-soluble	Oil-soluble
Works on	Skin surface	Skin surface + inside pore
Best skin type	Dry, normal, mature	Oily, acne-prone, combination
Photosensitizing	Yes (use PM + SPF next AM)	Less so, but still prefer PM use
Most common %	Glycolic 5–10%; Lactic 5–10%	Salicylic 0.5–2%
Gentlest option	Lactic or PHA	0.5% salicylic

Can You Use Both?

Yes — on different days. AHA and BHA target different concerns, so using an AHA on Monday/Thursday and a BHA on Tuesday/Friday covers both without daily acid use (which would over-exfoliate most skin types).

Some Korean products combine AHA + BHA + PHA in one formula (e.g., Some By Mi 30 Days Miracle Toner). These use lower concentrations of each acid to allow combined use.

Concentration Guidelines

AHA:

• 5–8%: gentle, daily use for most skin types
• 8–15%: effective for most concerns, 2–3x per week
• 15–30%: approaching peel territory — professional guidance recommended

BHA:

• 0.5%: gentle, daily use (some Korean formulas)
• 1%: standard effective range
• 2%: maximum OTC strength; use 2–3x per week max

Bottom Line

Dry, textured, or hyperpigmented skin: AHA. Oily, congested, acne-prone skin: BHA. Both concerns? Rotate. Start at the lowest effective concentration, use in the PM, and always follow with SPF the next morning [3]. Over-exfoliation is a more common mistake than under-exfoliation.

This article reflects current dermatological consensus and is not a substitute for personalized advice from a licensed dermatologist.