Lactobionic Acid

Lactobionic acid is a polyhydroxy acid (PHA) exfoliant/humectant typically used around ~2–10% (sometimes higher) at mildly acidic pH; it is generally better tolerated than glycolic/lactic acid due to its larger molecule and slower penetration. However, as an exfoliating acid it can still cause stinging, erythema, and barrier disruption in reactive or eczematous skin—especially when layered with retinoids, benzoyl peroxide, or other acids—so I score it as mild rather than “gentle” for high-risk patients. Safety Notes: In commercial skincare, lactobionic acid (a PHA) is found at very low levels (~0.1–1%) in sensitive-skin toners/serums and multi-acid formulas where it functions as a mild exfoliant/humectant alongside other acids. Most leave-on PHA products cluster around ~2–10%, while the highest consumer-available OTC strengths I’ve observed are ~12–15% in dedicated PHA resurfacing serums/creams marketed for at-home use (higher levels are uncommon due to tackiness, neutralization/pH control needs, and irritation risk even though PHAs are generally milder). Rinse-off cleansers typically sit on the lower end versus leave-on treatments, with performance driven heavily by finished-product pH and buffering rather than % alone.