Ingredients
AHA vs. BHA vs. PHA: Which Acid Does What — And Which One You Don’t Need
Skincare acids are not interchangeable. Each one solves a different problem. Most people need one — not all three.
AHAs
Alpha Hydroxy Acids · Water-soluble
Dissolve bonds between dead surface cells. Accelerate turnover, smooth texture, improve tone. Glycolic = smallest, most aggressive. Lactic = gentler, also a humectant. Mandelic = largest, often preferred for sensitive and darker skin tones.
⚠️ UV warning: AHAs increase sun sensitivity. SPF is required, not optional.
Best for: Texture, dullness, fine lines, sun damage
BHA
Salicylic Acid · Oil-soluble
The only acid that dissolves into sebum and follows it into the follicle. Breaks apart keratin plugs, helps with oiliness and pore congestion, and has notable anti-inflammatory effects. AHAs cannot do this — they stay on the surface.
Best for: Acne, blackheads, oiliness, congested pores
PHAs
Gluconolactone, Lactobionic Acid · Large molecules
Largest molecules, slowest penetration, least irritating. Humectant and mild antioxidant properties. Emerging rosacea data. Useful for genuinely sensitive skin — and if you already tolerate gentle AHAs, PHAs may be optional rather than essential, though they do add extra humectant and antioxidant benefits.
Best for: Truly reactive skin that can’t tolerate any other acid
The Decision Framework
Texture, dullness, fine lines, sun damage → AHA. Acne, blackheads, oiliness → BHA. Can’t tolerate either → PHA. Most people do best starting with one well-chosen acid rather than a whole rotation. Start 2–3× per week. Always moisturize after. Always SPF with AHAs.
Final Take
AHAs and BHA have overlapping benefits but different strengths — AHAs focus on the surface, BHA penetrates pores. PHAs exist for sensitive skin that struggles with either, and they add humectant and antioxidant benefits even if you tolerate gentler AHAs. The biggest mistake isn’t using the wrong acid; it’s using too many at once. One well-chosen acid, at the right concentration, at the right pH, used consistently with sunscreen, will outperform a cabinet full of exfoliants applied without strategy.
