The key difference: molecule size
- Glycolic acid is the smallest AHA. It penetrates fast and deep, which makes it effective for texture and fine lines but also the most likely AHA to cause stinging, redness, and irritation.
- Mandelic acid is one of the largest AHAs (derived from the same family as almonds, though Neutralyze uses a synthesized, nut-allergy-safe form). It penetrates slowly, exfoliating gently and uniformly.
Why this matters for darker skin tones
Irritation itself can trigger post-inflammatory hyperpigmentation (PIH) — the dark marks that medium and deep skin tones are especially prone to after breakouts or harsh products. Because mandelic acid exfoliates with far less irritation, it carries a lower risk of rebound dark marks, which is why it is widely regarded as one of the most pigmentation-friendly exfoliating acids. Glycolic acid, used aggressively, can make PIH worse on reactive or melanin-rich skin.Which should you choose?
- Acne-prone, sensitive, or darker skin: mandelic acid, ideally paired with salicylic acid (a BHA) to clear inside the pore. See Salicylic Acid vs. Mandelic Acid for how the two work together.
- Resilient skin focused purely on texture or fine lines, with no active breakouts: glycolic acid can work — start low and slow.