Ascorbic Acid
INCI: ASCORBIC ACID
Reviewed by Emma · Last updated 14 Aug 2026
A water-soluble antioxidant that helps defend skin against environmental damage and support collagen production
Best For Skin Types
All
Addresses
Effective Concentrations
5-20%
Usage Frequency
Daily
What Is Ascorbic Acid?
Ascorbic acid is the pure, active form of vitamin C. It is a water-soluble compound that acts as a potent antioxidant in skincare formulations. When applied topically, it helps neutralise free radicals generated by UV exposure and environmental stressors, which can otherwise contribute to skin ageing and damage.
Beyond its antioxidant role, ascorbic acid plays a part in the skin's natural collagen synthesis pathway. This dual function—protecting existing skin structures whilst supporting their renewal—makes it a frequently used ingredient in anti-ageing and brightening skincare products.
Benefits for Your Skin
How It Works
Ascorbic acid neutralises free radicals—unstable molecules created when skin is exposed to UV light and pollution. By donating electrons to these reactive molecules, it prevents them from damaging skin cells and collagen fibres, which would otherwise accelerate visible ageing.
The ingredient also participates in the enzymatic reactions required for collagen synthesis. This involves stabilising the enzymes responsible for cross-linking collagen molecules, which supports skin structure and resilience. However, the extent of these changes in human skin requires sustained, consistent use to become apparent.
Clinical Evidence & References
Research on topically applied ascorbic acid demonstrates antioxidant activity and measurable improvements in photoaged skin. A clinical study found that a 5% ascorbic acid cream applied daily over 6 months showed beneficial effects on sun-damaged skin on the neck and arms compared to placebo, with safety profiles comparable to the vehicle alone.
Absorption studies indicate that ascorbic acid penetrates skin most effectively at low pH (below 3.5) and at concentrations around 20%, with tissue saturation occurring after a few days of daily use. Evidence for benefits like pore minimising or scar healing is more limited; claims in these areas should be viewed as preliminary rather than established.
Published Research
How to Use
Ascorbic acid is most effective when formulated at a low pH (ideally below 3.5) to ensure adequate skin penetration. Products should be stored away from heat and light, as the ingredient degrades over time. Use daily for best results, typically in the morning as part of your routine before moisturiser and sunscreen. If combining with other actives, introduce gradually and monitor your skin's response, as some individuals may experience mild irritation initially.
Safety & Precautions
Frequently Asked Questions
From the Clinic
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Ascorbyl Dipalmitate
A stable vitamin C derivative that works as an antioxidant to help protect skin from environmental stress
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