Vitamin C (L-ascorbic acid)
Ascorbic Acid
A morning antioxidant that brightens, fades pigment, and boosts what your sunscreen is doing.
L-ascorbic acid neutralises free radicals generated by UV and pollution, which is why it belongs in the morning under sunscreen. It also interferes with pigment production and is a required cofactor for collagen synthesis. Its weakness is stability: it oxidises on contact with light and air, turning yellow then brown. A darkened bottle has lost potency and should be replaced.
How to use it
Morning, before sunscreen. Store away from light. Replace when it turns amber.
What it helps with
Pairing with other actives
Both are low-pH actives, and using them together raises the odds of stinging without adding benefit.
Vitamin C in the morning, acids at night.
Benzoyl peroxide oxidises vitamin C, wasting both.
Keep them in separate routines, morning and night.
You may have read that these cancel each other out. In modern formulations they do not.
The old warning came from 1960s research using raw, unstable forms at high heat. Layer them freely.
Both are potent and prefer different conditions; together they irritate more than they help.
Vitamin C in the morning under sunscreen, retinol at night. This is the standard pairing.
Products containing it
Related reading
What order to apply your skincare
Thinnest to thickest, with two exceptions that matter more than the rule itself.
How to introduce a new active without wrecking your skin
Most bad reactions come from starting too fast, not from the wrong product.
Fading dark spots and post-acne marks
Different causes need different treatment, and one of them is not pigment at all.
Ingredient conflicts: what's real and what's repeated
Some combinations genuinely cause problems. The most famous one does not.
Routine is educational and is not medical advice. Recommendations are generated from the answers you gave and general dermatological guidance — they cannot account for your full history. For persistent or severe skin conditions, or before starting anything new during pregnancy, speak to a doctor or dermatologist.