What is L-ascorbic acid and why does it matter?

L-ascorbic acid is the pure, active form of vitamin C that is directly usable by skin cells. It is the most researched form and offers the strongest antioxidant protection and brightening effects. However, it is also the least stable, oxidizing quickly when exposed to air, light, or heat. Formulations must include stabilizers like ferulic acid or vitamin E and be stored carefully to maintain potency.