Glycolic acid enhances skin penetration of kojic acid while itself promoting cell turnover and removing pigmented cells.
Glycolic acid penetrates deeper due to smaller molecular size, while lactic acid provides surface exfoliation plus hydration. Multi-level AHA exfoliation.
Sequential use: glycolic acid exfoliates and increases cell turnover; niacinamide follows to repair barrier and reduce inflammation.
BHA dissolves sebum inside pores while AHA loosens dead cells on the surface. Multi-level exfoliation for congested skin.
AHA exfoliation increases HA penetration into freshly revealed skin. HA also counteracts the drying effect of glycolic acid.
AHA exfoliation reveals fresh skin that absorbs vitamin C more effectively. Sequential use (AHA first, then C) boosts brightening results.
AHA exfoliation followed by panthenol repair. Glycolic promotes cell turnover, panthenol speeds recovery of exfoliated skin.
Both are potent actives that can cause irritation. Combined use increases risk of over-exfoliation, barrier damage, and sensitization.
Using two AHAs simultaneously at high concentrations increases risk of over-exfoliation. Low concentrations are fine (see synergy entry for blended products).
Prescription retinoid + strong AHA dramatically increases risk of chemical burns, severe irritation, and barrier destruction.
Low pH of AHAs can disrupt the copper-peptide complex, reducing its efficacy. Best used at different times.
Strong oxidizer + exfoliant causes excessive dryness and irritation. Should not be used simultaneously.
Both require acidic pH but at different ranges. Mixing can destabilize one or both. Better used at different times.
Kojic acid is unstable in acidic pH below 3 and near strong AHAs. Can darken and lose efficacy.
Using both strong acids can over-exfoliate and increase irritation. One acid at a time is recommended for sensitive skin.
Strong acids can break peptide bonds, reducing their efficacy. Peptides work best at neutral pH.
Retinoid + AHA combination increases irritation. Adapalene is more tolerable than tretinoin but still risky with strong AHAs.
Heavy occlusive petrolatum can trap glycolic acid against skin, increasing irritation risk and potential chemical burn.
Both increase photosensitivity. Combined without strict SPF protocol increases risk of rebound hyperpigmentation.
Retinal (retinaldehyde) is more potent than retinol. Combined with strong AHA, irritation risk is significant.
Retinoic acid ester + AHA can cause excessive irritation even though HPR is considered gentler than retinol.
Myth: "AHAs destroy ceramides." Actually, lactic acid promotes ceramide synthesis. Glycolic acid effects are neutral to mildly positive for ceramide production.
Myth: "AHA degrades hyaluronic acid on the skin." Applied HA and glycolic acid do not interact negatively at typical cosmetic concentrations.
Myth: "never use vitamin C with AHAs." Both prefer acidic pH and can work well together. The concern is over-sensitization in sensitive skin, not chemical incompatibility.
Myth: "panthenol neutralizes AHA effects." Panthenol soothes without interfering with glycolic acid exfoliation mechanism.