Vitamin C is the most researched topical antioxidant in skincare. L-Ascorbic Acid (L-AA) at 10-20% concentration neutralises free radicals, boosts collagen production, fades hyperpigmentation, and enhances photoprotection.
But Vitamin C is notoriously unstable. It oxidises rapidly in the presence of light, air, and water. The best formulations use stabilised derivatives or encapsulation technology.
| Form | Stability | Potency | Best For | |------|-----------|---------|----------| | L-Ascorbic Acid | Poor (oxidises fast) | Highest (gold standard) | Visible results | | Sodium Ascorbyl Phosphate (SAP) | Good | Moderate | Acne-prone skin | | Ascorbyl Glucoside | Good | Moderate | Sensitive skin | | Tetrahexyldecyl Ascorbate | Excellent | Good | Dry skin, pairing with retinol | | Ascorbyl Palmitate | Moderate | Lower | Formulation stability |
Morning routine:
Frequency: Daily, morning. Vitamin C boosts sunscreen efficacy by neutralising free radicals.
Storage: Keep in a cool, dark place. Refrigerate after opening. Discard if it turns dark yellow/brown (oxidised).
Can I use Vitamin C with retinol? Yes, but at different times. Vitamin C in the morning, retinol at night.
What concentration should I use? Beginners: 5-10%. Experienced: 15-20%. L-AA maximum efficacy is at 15-20%.
Why did my serum turn brown? It has oxidised. Oxidised Vitamin C is not harmful but has lost efficacy. Replace it.
Sources: Journal of the American Academy of Dermatology, International Journal of Cosmetic Science, British Journal of Dermatology.
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