Vitamin C in Cosmetics: Everything You Need to Know to Choose the Right Product

Vitamin C is the most sought-after antioxidant ingredient in cosmetics—and one of the most misused. There are many forms of vitamin C, each with vastly different levels of efficacy, stability, and tolerability. Here’s how to navigate this complex landscape using real clinical data.

The different forms of vitamin C

Ascorbic acid (L-ascorbic acid) is the most potent form of vitamin C, but also the most unstable. It oxidizes quickly when exposed to air and light, and can cause irritation, especially on sensitive skin.

Ascorbyl Glucoside, on the other hand, is a more stable and gentler form. Once absorbed by the skin, it is gradually converted into ascorbic acid by skin enzymes. It is extremely well-tolerated, making it suitable for all skin types, including the most sensitive. This is the form we have chosen for Ritual 02.

Why not choose ascorbic acid?

The choice of ascorbyl glucoside is not a compromise, but a deliberate formulation decision. Our anti-blemish, wrinkle-preventing serum was designed for sensitive and reactive skin, whereas pure ascorbic acid generally requires a very acidic pH—around 3—to be fully effective, which can weaken the skin.

Our biomimetic formulas are developed with a physiological pH between 5.5 and 6.5 to preserve the natural balance of the skin barrier. This pH level is better suited for ascorbyl glucoside than for pure ascorbic acid.

What Vitamin C Actually Does for Your Skin

Vitamin C has three major clinically documented benefits. First, it acts as an antioxidant by neutralizing the free radicals responsible for oxidative stress. It also helps inhibit melanogenesis, which helps reduce the appearance of dark spots. Finally, it stimulates collagen production, thereby helping to improve skin firmness.

The most immediately noticeable effect is usually an even skin tone and improved radiance, which are often visible after 2 to 4 weeks of regular use.

Vitamin C and niacinamide: Are they compatible or not?

Yes, vitamin C and niacinamide are perfectly compatible in well-designed modern formulations. The notion that these two active ingredients are incompatible stems from older studies conducted with pure ascorbic acid at very high concentrations under unstable conditions.

The current formulations, which are more stable and better balanced, do not have this problem.

Should I use it in the morning or at night, and what ingredients should I combine it with?

Vitamin C is best used in the morning, under sunscreen, to provide additional antioxidant protection against environmental stressors throughout the day.

It works particularly well in combination with niacinamide, peptides, ceramides, and hyaluronic acid.