Pure Vitamin C (INCI: Ascorbic Acid) is one of the most studied cosmetic actives, with efficacy documented in numerous clinical studies at concentrations from 5 to 20%. Available scientific data associate it with several properties.
Antioxidant properties: multiple studies link vitamin C to antioxidant activity that helps protect skin from environmental factors (sun, pollution) and visibly reduce redness after exposure. Morning application is recommended. The combination of vitamin C + sun protection is associated, according to available data, with a better overall protective profile.
Support for skin structure mechanisms: associated, according to available data, with normal collagen formation to ensure normal skin function (EFSA-authorized nutrition claim) and, in cosmetics, with firmness appearance and visible reduction of fine lines. Clinical studies documented for concentrations of 5 to 10%.
Even skin tone: vitamin C is linked to regulating melanogenesis (tyrosinase enzyme) and visibly reducing pigment irregularities.
Limitations of pure vitamin C: sensitivity to oxidation, limited penetration in its free form, potentially irritating at acidic pH. This is why stabilized derivatives are often used.
The best-studied in vivo derivatives are as follows. Ascorbyl Tetraisopalmitate is a stable liposoluble derivative, well studied for its penetration and antioxidant properties. Ascorbyl Glucoside is stable, associated according to available data with the three vitamin C properties (antioxidant, skin structure support, visible reduction of pigment irregularities), generally used at 2 to 5% for radiance and visible reduction of pigment irregularities. Ethyl Ascorbic Acid (EAC) is stable and associated, according to available data, with skin penetration. It is documented for antioxidant and soothing activity, as well as supporting mechanisms involved in maintaining skin structure. At 2%, it is linked to visible improvement of skin tone.
⚠️ Not recommended combination: do not use simultaneously with skincare containing copper peptides (Copper Tripeptide-1). Vitamin C can oxidize the copper in these peptides, reducing the efficacy of both actives. If using both, reserve vitamin C for morning and copper peptides for evening.
Sources: Stability, transdermal penetration, and cutaneous effects of ascorbic acid and its derivatives, Journal of Cosmetic Dermatology, 2012; Assessment of penetration of Ascorbyl Tetraisopalmitate into biological membranes, Computers in Biology and Medicine, Vol. 75, 2016.
