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THD Ascorbate (Lipid Vitamin C) and Retinol: Why Oil-Soluble Vitamin C Works at pH 5.5
Unlike L-Ascorbic Acid (pH 3.2), Tetrahexyldecyl Ascorbate is stable at pH 5.5–6.0, eliminating the ΔpH conflict with Retinol.
Recommended Spacing: 5 Minutes
Apply THD Ascorbate 15% in the AM under SPF 50 for deep lipid-bilayer photoprotection.
Apply Retinol in PM (or co-layer with THD Ascorbate on resilient skin).
Layering low-pH keratolytic acids (pH 3.0–3.8) with nuclear retinoids strips the stratum corneum barrier, accelerates acid-catalyzed retinoid degradation, and causes severe retinoid dermatitis.
- AM Prep: pH 5.5 Gentle Amino-Acid Cleanser or Water Rinse [pH 5.5 · Pat dry]
- AM Barrier + Photoprotection: Physiological Ceramide Moisturizer + Broad-Spectrum SPF 50+ PA++++ [pH 5.8 · Mandatory final step]
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Esthetician & Cosmetic Chemist FAQ
Can you layer THD Ascorbate (Lipid Vitamin C) and Retinol (Vitamin A) in the same skincare routine?
Unlike L-Ascorbic Acid (pH 3.2), Tetrahexyldecyl Ascorbate is stable at pH 5.5–6.0, eliminating the ΔpH conflict with Retinol. Recommended protocol: Apply THD Ascorbate 15% in the AM under SPF 50 for deep lipid-bilayer photoprotection. Apply Retinol in PM (or co-layer with THD Ascorbate on resilient skin).
What is the ΔpH between THD Ascorbate (Lipid Vitamin C) and Retinol (Vitamin A)?
The formulation pH differential is approximately ΔpH 0.3 (4.5–6.5 vs 5.5–6.5). Any ΔpH > 1.8 shifts Henderson-Hasselbalch free-acid bioavailability or stresses acid-labile bonds.
How long should I wait between Tetrahexyldecyl Ascorbate and Retinol?
Allow a 5-minute acid-mantle equilibration window on dry skin before applying the second layer.