AHAs and BHAs: Choosing the Right Exfoliant for Your Skin Type

What AHAs and BHAs Actually Do

Chemical exfoliants work by loosening the bonds that hold dead skin cells together, allowing them to shed more efficiently than physical scrubbing. AHAs (alpha hydroxy acids) and BHAs (beta hydroxy acids) are the two main categories, and while both exfoliate, they do so in meaningfully different ways — a distinction that matters when you're matching an exfoliant to your skin's actual needs.

AHAs are water-soluble acids derived primarily from natural sources. Glycolic acid, sourced from sugarcane, and lactic acid, derived from milk, are the two you'll encounter most often. Because they are water-soluble, AHAs work predominantly at the skin's surface, breaking apart dead cell bonds in the outermost layer. This makes them effective for improving surface texture, evening skin tone, and supporting the skin's ability to hold moisture. Some research also suggests certain AHAs stimulate collagen production, though this is an area of ongoing study.

BHAs are oil-soluble. Salicylic acid — a derivative of willow bark — is by far the most common BHA used in skincare. Its oil solubility is the key functional difference: rather than staying on the surface, salicylic acid can travel through the sebum that fills a pore and work inside it. This makes BHAs uniquely suited to addressing blackheads, whiteheads, and breakouts rather than surface-level concerns alone.

Before diving deeper into which acid suits which skin type, it helps to know your own skin type accurately. Our guide on identifying your skin type walks through the signs of each clearly.

Matching the Right Acid to Your Skin Type

Dry and mature skin generally benefits most from AHAs. Dead cell buildup on dry skin contributes to a rough, dull surface, and AHAs — particularly lactic acid — help clear that buildup while also drawing water into the skin. Glycolic acid, with its smaller molecular size, penetrates more efficiently but can be more irritating, so starting with lactic acid is often the more comfortable entry point.

Oily and acne-prone skin is where BHAs shine. Salicylic acid's ability to penetrate into pores and dissolve oil-based debris makes it far more effective than surface-only exfoliation for addressing congestion and breakouts. It also has recognized anti-inflammatory properties, which can help calm the redness associated with active acne.

Combination skin is trickier. A gentle AHA used across the full face is often a practical starting point. Some people apply a BHA only to the oilier zones — typically the nose and chin — rather than everywhere. Alternating between the two on different nights is another common approach, though it requires close attention to how skin responds.

Sensitive skin calls for particular caution with both acid types. Low-concentration lactic acid formulas — typically around 5% or below — are the gentlest starting option. Regardless of skin type, introduce any new exfoliant slowly: once a week to start, increasing frequency only if skin tolerates it well. Watch for signs of over-exfoliation, including persistent redness, tightness, and increased sensitivity, which our article on over-exfoliating and skin barrier damage covers in detail.

How to Use Chemical Exfoliants Safely and Effectively

A few ground rules apply regardless of which acid you choose. Both AHAs and BHAs increase photosensitivity — your skin becomes more vulnerable to UV damage after use. Applying a broad-spectrum sunscreen with SPF 30 or higher every morning is essential when using either type, not optional.

Most chemical exfoliants are best applied in the evening to freshly cleansed skin, before moisturizer. Where they fit in a broader routine matters. Because these are active, lower-pH products, they should generally be applied before heavier or more occlusive products. Our guide on skincare layering principles explains the logic of product sequencing in detail.

Avoid combining AHAs and BHAs in the same application session unless a product is formulated to do so. Layering multiple actives raises the risk of irritation significantly. If you want to use both types, alternate them on different evenings rather than stacking them. The same caution applies to using chemical exfoliants alongside other strong actives like retinol — give your skin time to adjust before adding complexity.

Finally, start with a lower concentration than you think you need. A 5–8% glycolic acid or a 1–2% salicylic acid is a reasonable starting range for most adults new to chemical exfoliation. Results from consistent, moderate use over weeks are more meaningful — and much safer — than aggressive, frequent applications.

This article is for general informational and educational purposes only. It does not constitute medical or dermatological advice. If you have a skin condition or persistent concerns, consult a qualified dermatologist or healthcare professional before introducing new active ingredients into your routine.