Vitamin C for skin

Limit certain oxidation reactions

The skin naturally contains vitamin C. It contributes to its antioxidant defenses by donating electrons to certain reactive molecules, which helps limit chain oxidation reactions. UV rays notably promote the formation of these reactive species, capable of damaging cellular constituents. Properly formulated treatment seeks to locally reinforce this reserve, without being able to neutralize all the consequences of exposure.

This action is different from that of sunscreen. Sun filters reduce the amount of UV rays that reach the skin; Antioxidants intervene in some of the reactions that these UV rays can trigger. In a study on human skin published in 2008, a precise formula of vitamins C and E with ferulic acid reduced several markers of damage after irradiation. This result supports their complementarity, but does not assign an SPF to all vitamin C serums.

Help make functional collagen

Vitamin C serves as a cofactor for enzymes necessary for collagen maturation, including those that modify certain proline and lysine residues. These steps allow the protein to acquire a stable structure. This explains the importance of vitamin C for skin resistance and healing.

Trials of topical vitamin C have observed improvements in texture or fine wrinkles after several months. The hydration provided by its base can also temporarily smooth the appearance of the skin, regardless of a slower modification of its collagen.

Act on certain pigmentary irregularities

Melanin is the pigment that contributes to skin color. Vitamin C can interfere with certain stages of its production, particularly around the activity of tyrosinase, and reduce certain oxidized intermediates of this synthesis. This is one of the reasons why it is used in treatments for spots and uneven skin tone.

A systematic review published in 2023 brings together seven publications, for 139 volunteers in total, on melasma and photoaging. It notes favorable results on pigmentation and certain signs of aging, while emphasizing the need for additional studies. The protocols and formulas differ: we cannot therefore deduce an ideal percentage valid for everyone, nor promise each user the disappearance of their spots.

Why the shape and the bottle change the result

L-ascorbic acid is water-soluble, while the stratum corneum constitutes a difficult barrier to cross. In classic experimental work on porcine skin, a pH below 3.5 favors its penetration and maximum absorption is observed around 20%. These are results obtained with certain formulations, not an instruction to systematically choose the most acidic or concentrated serum.

Derivatives modify the molecule to improve certain properties, such as its stability or its affinity with the formula. Their activity then depends on their penetration, their possible transformations in the skin and their specific properties. They are therefore not interchangeable. A 15% derivative serum is neither automatically stronger nor automatically less effective than a 10% ascorbic acid serum: the finished product must be evaluated on its own.

Air, light and heat can accelerate the breakdown of ascorbic acid. The packaging and the ingredients surrounding it therefore influence the quantity still available over time. Certain antioxidant associations, including vitamin E and ferulic acid, have been the subject of interesting studies. However, their presence on a label is not enough to reproduce a studied formula: proportions, stability and vehicle also count.