Glycolic acid penetrates deeper due to smaller molecular size, while lactic acid provides surface exfoliation plus hydration. Multi-level AHA exfoliation.
Lactic acid promotes ceramide synthesis in the stratum corneum. Exogenous ceramides further enhance barrier repair after acid exfoliation.
Both are natural moisturizing factor (NMF) components. Urea hydrates and mildly exfoliates, lactic acid provides additional AHA exfoliation and ceramide-boosting.
Lactic acid exfoliates gently while providing humectant properties. Combined with HA for hydrating exfoliation.
Using two AHAs simultaneously at high concentrations increases risk of over-exfoliation. Low concentrations are fine (see synergy entry for blended products).
Lactic acid low pH may destabilize retinol and increase irritation risk. Better alternated AM/PM.
Prescription retinoid + AHA is a strong combination that significantly increases irritation and barrier disruption risk.
BHA + AHA at high concentrations leads to excessive exfoliation and significantly increases irritation risk for most skin types.
BP + AHA combination increases dryness and irritation risk significantly. Both are strong actives best used separately.
Retinoid + AHA combination increases skin sensitivity and peeling risk. Better alternated.
Unspecified type