Ingredient library / Antioxidant
Vitamin C.
Also on labels as: L-ascorbic acid · Ascorbic acid · Tetrahexyldecyl ascorbate · 3-O-ethyl ascorbic acid · Ascorbyl glucoside
Quick answer
What is vitamin c?
Vitamin C is an antioxidant used in serums to help skin look brighter and more even, and to support protection against environmental damage alongside sunscreen. Pure L-ascorbic acid is the most studied form but the least stable; derivatives are gentler and more stable, though evidence for them is more limited.
What it does
- Antioxidant support that complements, but never replaces, sunscreen
- Helps the look of dullness and uneven tone
- Plays a role in collagen production in skin
Who it suits
Most skin types looking for brightness. Sensitive skin may prefer a derivative or a lower-strength formula.
How to use it
- Usually applied in the morning after cleansing, before moisturiser and sunscreen
- Store as directed — many formulas degrade with air, light and heat
- Discard if a pure L-ascorbic acid serum turns dark orange or brown
Take care
- High strengths of L-ascorbic acid can tingle or sting
- Patch test if you have sensitive skin
What it pairs with
Works well with vitamin E and ferulic acid, and before sunscreen. Keep strong exfoliating acids and retinoids for the evening unless a product says otherwise.
General information, not medical advice. For a skin condition, pregnancy or persistent irritation, speak to a pharmacist, GP or dermatologist.
In the catalogue
Products listing vitamin c.
SkinCeuticals · Skin prep
C E Ferulic
The L-ascorbic acid benchmark: a clear, light morning layer that sits under sunscreen and base without adding shine.
Medik8 · Skin prep
C-Tetra
A water-free vitamin C layer for morning prep — a fine oil to let settle before sunscreen and base.
The Ordinary · Skin prep
Vitamin C Suspension 23% + HA Spheres 2%
An evening vitamin C step, kept away from the morning base while its granular texture absorbs.
Beauty of Joseon · Skin prep
Light On Serum: Centella + Vita C
A light, non-sticky vitamin C layer that settles quickly under sunscreen — the K-beauty option in the brightening edit.
Read further
Sources.
Vitamin C, answered
Should vitamin C be used morning or night?
- Most people use it in the morning, under sunscreen, for its antioxidant role. Follow the directions on your specific product.
What is the most effective form of vitamin C?
- L-ascorbic acid has the most research behind it but is unstable and can irritate. Derivatives such as tetrahexyldecyl ascorbate and 3-O-ethyl ascorbic acid are more stable and usually gentler.
Why did my vitamin C serum turn orange?
- L-ascorbic acid oxidises when exposed to air, light and heat, which darkens the serum. A strongly darkened serum is past its best.