Cos De Baha — VA Vitamin C 15% Pure Ascorbic Acid Serum 30ml

Cos De Baha's VA Serum is the most directly active vitamin C formula in their selection. The 15% Ascorbic Acid (L-AA) is the gold standard form: it works directly without metabolic conversion, with documented antioxidant, depigmenting, and collagen synthesis-supporting efficacy at this concentration. A pH of ~3 is necessary for the molecule's stability and for its non-ionized form, which penetrates lipid membranes—but it contributes to a higher irritating potential than derived forms (SAP, MAP, ascorbyl glucoside). Propanediol as the first ingredient (before water) improves the solubility and penetration of ascorbic acid, and is an optimized solvent for low-pH VitC formulas. Arbutin (beta-arbutin, fourth position) provides secondary tyrosinase inhibition, complementing the direct action of L-AA. Arginine partially buffers the pH. Panthenol compensates for potential irritation. Critical stability point: ascorbic acid gradually oxidizes—an expiration date of 07/2027 means approximately 14 months remaining on unopened units. After opening, exposure to air accelerates oxidation. A VA serum that turns dark yellow to brown-orange has lost some of its activity. Store in a cool, dark place, and seal tightly. Compatibility with niacinamide: the L-AA + niacinamide → nicotinic acid reaction documented in the laboratory requires prolonged heat conditions not reproduced in skin application. Recent literature considers the combination safe under normal use conditions. As a precaution and for simplicity, alternate morning (VitC) and evening (niacinamide). Do not use in the evening—risk of cross-sensitization with retinol and cumulative irritation.