Most vitamin C found in serums is L-Ascorbic acid. However, if you can, get the Tetra form which is Tetrahexyldecyl ascorbate, you may be much better off for it. It is known to penetrate deeper into the skin and it’s also less irritating. Although it’s much more expensive to use in a formula, it is being used more each year by the higher end cosmetic industry.
Tetrahexyldecyl Ascorbate is a stable, oil-soluble form of Vitamin C, used for anti-aging because of its ability to increase collagen levels, reduce melanin production, brighten skin, and repair the effects of UV exposure and other environmental damage. You won’t find this version in water based serums. It’s soluble in oil and that is one of the reasons it can penetrate better to deeper layers of the skin.
L-ascorbic acid does better in a water based solution but is not known to penetrate deeper into the skin layers, it only treats the top layer.
In our Fleurs de France oil based Night Serum we use the Tetra version. Look for it when you’re buying an oil based serum.