Carnosine is a small peptide made up of 2 amino acids. It occurs naturally in the body, especially in the muscle and nerve tissues where it is synthesised (R). It has been associated for a long time with antiageing and cellular longevity (R), which are though to be linked to its antioxidant, anti-glycation and metal ion chelating activities (R).
Carnosine has been shown to penetrate full-thickness human skin, with some reaching the viable epidermis within just 30 minutes after application. The addition of propylene glycol enhances its penetration, increasing the concentration of carnosine detected in the epidermis and dermis and more than tripling the detectable concentration from <5% of the applied dose to close to 18% (R). A separate preliminary study indicated that compared to free carnosine, a carnosine-magnesium complex may be superior at delivering carnosine to the lower skin layers (R).
Carnosine is not stable in the skin (R), possibly because it is hydrolysed by the enzyme carnosinase, which is present in most tissues in the body except the skeletal muscles (R).