Serum in cream form based on 10% ascorbic acid: an exceptionally high dose of the most effective, because skin identical form of vitamin C. Ascorbic acid is the only form of vitamin C that occurs naturally in the skin; it is therefore immediately recognized and absorbed by the skin. Indeed, like other forms of vitamin C, it does not first need to be converted by the skin to "recognizable" ascorbic acid. Moreover, ascorbic acid-based products cannot cause allergic reactions: after all, it is skin identical. Another plus: ascorbic acid is the most stable form of vitamin C. Normally, vitamins lose their activity when exposed to light, air or water. Ascorbic acid does not. It is the only type of vitamin C that remains completely stable and intact as long as it does not come into contact with water. Incorporating ascorbic acid into an anhydrous cream creates a product that is 100% stable, active and effective from first use to last. The vitamin C is released only upon contact with moisture present in the skin.