AHAs vs BHAs: Chemical Exfoliation Explained
The difference between alpha and beta hydroxy acids, which skin concerns they target, how to use them safely, and what to avoid combining them with.
Chemical exfoliants dissolve the bonds holding dead skin cells together, revealing fresher skin underneath without the micro-tears that physical scrubs can cause. They split into two families: AHAs work on the skin's surface and are water-soluble; BHA (salicylic acid) is oil-soluble and can penetrate into pores. Both require an acidic pH (below 4.5) to be effective.
AHAs vs BHA at a glance
- Glycolic acid (AHA): smallest molecule, deepest surface penetration, most evidence for fine lines and dullness. Can be irritating for sensitive skin.
- Lactic acid (AHA): gentler than glycolic, also mildly hydrating, good starting point for AHA beginners.
- Mandelic acid (AHA): largest molecule, slowest penetration, gentlest AHA — well suited to sensitive or darker skin tones.
- Salicylic acid (BHA): penetrates sebum, gets inside pores, reduces blackheads and inflammatory acne. Best choice for oily and acne-prone skin.
- Do not layer AHAs/BHAs with retinoids on the same night — too much acid disruption risks barrier damage. Alternate nights instead.
- Always apply SPF the morning after using any exfoliant — freshly exfoliated skin is more UV-sensitive.
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