Maximum Vitamin C Concentration

A well-informed lady commented today regarding the maximum possible concentration of Vitamin C in L-Ascorbic Acid form in a cosmetic product. Naturally, the answer depends on the form the cosmetic product takes. A product may be stricitly in powder form, in which case, it can be 100% L-Ascorbic Acid, as is the case in many brands' offerings. This powder, however, must be first diluted or somehow mixed in a liquid formulation to be applied to the skin and absorbed, so we will disregard this form. The other possibility is to dilute the Vitamin C in a water-based formulation. The maximum possible concentration of L-Ascorbic Acid in water is just higher than 33%, above which level such solubility is chemically unfeasible in a topical formulation. Water-based formulations, however, are not suitable for Vitamin C treatments, because the active is oxidized in water and turns orange in colour. At that time, the antioxidant potential of Vitamin C turns into a prooxidant potential -- the exact opposite effect than intended. In water-free formulations, however, Vitamin C is completely stable in its pure free form and does NOT require any other antixodiants (Vitamin E, Alpha Lipoic Acid, L-Cysteine, etc.) to form an antioxidant network to maintain its stability over time. Depending on the particle size, concentrations more than 18% become very difficult to achieve in these types of formulations and more than 23% becomes almost impossible. Interestingly, 23% appears to also offer the optimal concentration as a topical. A particular study compared the effects of a 23% solution against a 20% solution with surprisingly significant efficacy improvement.

The well-respected Journal of Cosmetic Dermatology has published an article on this topic: it can be downloaded from this link: www.complex31.com/articles/JCD-T2-Asc-Immi.PDF.