Chemical Exfoliation Guide: AHAs vs BHAs vs PHAs

AHAs (Alpha-Hydroxy Acids): Water-soluble acids that exfoliate the skin surface. Best for texture, fine lines, hyperpigmentation, dullness. Key members: Glycolic acid (strongest, smallest molecule), Lactic acid (gentler, moisturizing), Mandelic acid (gentlest, good for acne-prone and darker skin).

BHAs (Beta-Hydroxy Acids): Oil-soluble acids that penetrate into pores. Best for acne, blackheads, oily skin. Key member: Salicylic acid (the only commonly used BHA).

PHAs (Poly-Hydroxy Acids): Large-molecule acids that work very slowly on the surface. Best for extremely sensitive skin. Key members: Gluconolactone, Lactobionic acid. Humectant properties. Minimal irritation.

Oily/acne-prone skin: Salicylic acid 0.5-2%. Add glycolic acid 5-10% for texture improvement.

Dry/aging skin: Glycolic acid 5-10% or Lactic acid 5-10% for surface exfoliation and hydration.

Sensitive skin: Mandelic acid 5-10% or PHA (gluconolactone 4-10%). These penetrate slowly and cause less irritation.

Dark skin tones: Mandelic acid or azelaic acid. Glycolic acid can trigger post-inflammatory hyperpigmentation in darker skin types if used too aggressively.

All skin types: Start with the lowest concentration, use every other night, and increase frequency over 4 weeks. Always use SPF — exfoliated skin is more sun-sensitive.

Over-exfoliation is the most common skincare mistake with acids. Signs include:

- Persistent redness or burning (not temporary tingling) - Tight, waxy-looking skin - Increased sensitivity to products that were previously fine - Breakouts in unusual areas - Skin looks shiny but feels dry

If you are experiencing these, stop all exfoliating products and actives. Use only gentle cleanser, basic moisturizer (ceramides), and sunscreen for 2-4 weeks until the barrier recovers. Then reintroduce acids at a lower frequency.