Vitamin C

Vitamin C is one of the most effective brightening ingredients in skincare — and one of the easiest to waste money on if you don't know how unstable it is. Here's how to actually get results from it.

L-ascorbic acid vs. the derivatives

L-ascorbic acid is the gold standard — the most-studied, most potent form, effective at 10–20%. It's also unstable: it oxidises with exposure to light, air and heat, and a serum that's turned yellow or brown has already degraded and lost most of its potency. Derivatives — magnesium ascorbyl phosphate, sodium ascorbyl phosphate, THD ascorbate, ascorbyl glucoside — are more stable and gentler, requiring conversion to active vitamin C once on skin. They're the better choice for sensitive skin or as a first vitamin C product.

How it actually works

Three mechanisms at once: it neutralises free-radical damage from UV and pollution as an antioxidant, it inhibits the enzyme that triggers melanin production (which is why it fades dark spots and evens tone over time), and it's a required cofactor for the enzymes that build collagen. None of this is instant — expect 4–8 weeks of consistent use before you see a real difference in tone.

Storage matters more than the brand

Keep it in a cool, dark place, away from your bathroom windowsill (light and heat are what kill it). Opaque or amber packaging is worth paying for. If a serum arrives clear or pale yellow and slowly darkens over weeks, that's oxidation in progress — it still has some efficacy but less than day one.

What to pair it with

Vitamin E and ferulic acid stabilise vitamin C and boost its antioxidant effect — this is the classic combination for a reason. Always follow with SPF; vitamin C and sunscreen work as a team, one neutralising damage, the other blocking it. If you also use strong acids, stagger them across AM/PM rather than layering both at once, since stacking multiple low-pH actives can tip sensitive skin into irritation.