We present here a new cosmetic formula system containing 3% ascorbic acid based on an optimized oil-in-water (O/W) emulsion. This formulation demonstrated a good long-term stability of the active ingredient and also of the emulsion itself. It could be deduced from in vitro release studies that this O/W emulsion enabled a better release of the hydrophilic active agent than an alternative W/O emulsion. By measuring the ultraweak photon emission, which is a well-established parameter for the oxidative stress in the skin, the high in vivo antioxidant capacity of 3% ascorbic acid was demonstrated after 1 week of product application. This placebo-controlled study also proved that ascorbic acid in an O/W cream reduced oxidative stress in human skin significantly better than the derivative sodium ascorbyl-2-phosphate, a more stable vitamin C replacement commonly used in cosmetic formulations. With increasing age, the number of papillae in the epidermal-dermal junction zone in human skin are reduced. This implies a possible consequence of reduced mechanical resistance of the skin and impaired supply of the epidermis with nutrients. In a 1-month placebo-controlled study on 25 human volunteers, a significant increase in the number of dermal papillae after application of the 3% ascorbic acid cream was demonstrated, using a confocal laser scanning microscope. Fine lines and wrinkles are a characteristic sign of aged and especially photo-aged skin. Application of 3% ascorbic acid in a 12-week placebo-controlled usage study indicated a significant reduction of facial wrinkles. Altogether, 3% ascorbic acid in a cosmetic O/W emulsion has been shown to be appropriately stable and to enable a good release of the active agent in vitro as a precondition for a high efficacy in vivo. Application in vivo resulted in a significant reduction of oxidative stress in the skin, an improvement of the epidermal-dermal microstructure and a reduction of fine lines and wrinkles in aged skin. These results were received within a relatively short period of time of product application.

Taken together, these results show that the combination of folic acid and creatine significantly accelerates epidermal skin regeneration in vitro and in vivo. Together with the finding of improved biomechanical skin properties, we conclude that the described topical formulation provides an effective treatment option for (photo)-aged skin.