Vitamin C in Skincare: What the Research Actually Shows

Vitamin C is one of the most studied skincare ingredients. It also has a frustrating tendency to oxidise, smell strange, and disappoint. This guide shows you how to use it correctly.

L-ascorbic acid — the active form of Vitamin C used in skincare — has a remarkable body of research behind it. It is one of only a handful of ingredients in cosmetics with clinical trials demonstrating visible improvement in skin appearance. It also has a reputation for being frustrating to formulate and unstable in use.

What Vitamin C Does in Skin

• Inhibits tyrosinase — the enzyme that produces melanin — leading to gradual brightening

• Neutralises free radicals from UV exposure and pollution (antioxidant function)

• Stimulates collagen synthesis — relevant for fine lines and firmness

• Enhances SPF effectiveness when used together in the morning routine

• Reduces visible pigmentation including post-inflammatory hyperpigmentation

The Stability Challenge

Pure L-ascorbic acid is unstable. It oxidises rapidly when exposed to air, light, and water — turning the serum yellow, then brown. An oxidised Vitamin C product is not only ineffective, it can be pro-oxidant, meaning it creates the free radicals you were trying to fight.

Derivatives as Alternatives

Ascorbyl Glucoside, Sodium Ascorbyl Phosphate, and Ascorbyl Tetraisopalmitate are stable derivatives that convert to L-ascorbic acid in the skin. They are gentler, more stable, and suit sensitive skin better. The trade-off is that they are slower and less potent than direct L-ascorbic acid.

Vikram Nair

Clinical Research Lead

This article was reviewed and written by an OLOOK expert. Our editorial team maintains editorial independence from commercial considerations.