Vitamin C plays a very important role in preventing and correcting skin damage when applied topically on a daily basis.L'-ascorbic acid is respected as the most valuable form of Vitamin C for skin because the skin contains l-ascorbic acid and specifically uses this form of Vitamin C to protect and repair itself from damage. Because the skin contains and uses l-ascorbic acid, it immediately recognises and uses it readily without the need to convert it to any other form of Vitamin C – so it is100% bioavailable within the skin. Other forms of Vitamin C need to convert to l-asorbic acid in the skin. However, the skin can’t efficiently convert other forms of Vitamin C ,therefore, bioavailability is greatly reduced with other derivatives.
L'-ascorbic acid has a small enough molecular weight to enter the epidermis, by lowering the pH to a range of 2.5-3.5, penetration is optimized. A pH below 2.5 can be irritating while a pH above 3.5 is less effective. Dermatol Surg Feb 2001