Actives Measured Against Claims

Why claim match carries more weight here

A serum is a concentrated leave-on product built around one or two actives. That makes it easier to judge than a cleanser, because the label tells you what it should do: fade marks, smooth texture, reduce oil. It also makes it easier to oversell. A "20% vitamin C" serum sounds strong, but the form of vitamin C, the pH and the packaging decide whether that percentage does anything once the bottle has been open for a month.

For serums, our claim-match score asks a narrow question: did the panel see the specific change the brand promised, within the timeframe the brand promised? If a niacinamide serum claims visibly smaller pores in two weeks, we photograph panellists under the same light at day zero, day fourteen and day twenty-eight. Photos are not a dermatology instrument, and we say so. But they keep us honest about whether anything changed beyond what anyone would notice after a month of good moisturising.

Concentration is not the same as quality

Higher is not automatically better. Niacinamide is well studied at around 2–5%, and many people tolerate 10%, but some report flushing at high concentrations. L-ascorbic acid, the most researched form of vitamin C, works best at low pH, which can sting. Retinol at 0.3% may irritate a beginner more than a 1% formula with an encapsulated delivery system would. Our formula score rewards sensible concentrations, stable forms and supportive ingredients, not headline numbers.

We also check packaging closely for this category. Vitamin C and retinoids degrade with light and air. A clear dropper bottle that lets air in every time you use it will lose potency faster than an opaque airless pump. When a serum turns orange or brown, it has oxidised; we note whether that happened during testing.

Patch-test first, always

Every panellist patch-tested each serum on the inner arm for 48 hours before facial use. Our sensitive-skin tester stopped two products early, and when that happens it lowers the tolerance score and is stated on the sheet. If you are pregnant or breastfeeding, speak to a doctor or pharmacist before using retinoids; the NHS and the American Academy of Dermatology both advise caution.