Vitamin C (L-ascorbic acid at pH 2.5–3.5) can hydrolyse or destabilise certain peptides, so combination in a single formula requires careful pH management or separate product formats such as a two-step regimen. Retinol is generally compatible with peptides at neutral-to-slightly-acidic pH. Always conduct a formal compatibility screen before finalising the formula. Cosmetic chemists available on AJ Cosmo Labs routinely handle multi-active compatibility work.
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