ISDIN Flavo-C Intense Explained: A Two-Phase Serum With 15% Vitamin C in Three Forms

ISDIN, the Barcelona-based dermatology brand, has been promoting Flavo-C Intense, a stronger sibling to its long-running Flavo-C serum. Marie Claire Argentina covered the product this week, and the brand's own product pages describe it as a 50 ml biphasic, or two-phase, anti-ageing serum meant for morning use. It is already stocked by European pharmacies, so this is a wider push rather than a brand-new global debut.

The headline figure is 15% vitamin C, but it is not a single ingredient. ISDIN splits it across three forms in what it calls the Tri-Antiox Complex: L-ascorbic acid, the water-soluble derivative 3-O-ethyl ascorbic acid, and ascorbyl tetraisopalmitate, an oil-soluble ester. The brand pairs these with three supporting antioxidants: hinokitiol, levulinic acid and vitamin E. Retailer ingredient lists also show hyaluronic acid, sodium metabisulfite (a common antioxidant preservative), alcohol and added fragrance. The page does not say how the 15% divides between the three forms.

The two-phase format is the main design choice. The two layers sit apart in the bottle, and users dispense two pumps into the palm and mix them before applying. Keeping parts of a formula separated until use is one way brands try to slow the breakdown of vitamin C, which is sensitive to water, air and light.

ISDIN's claims rest on its own unpublished data from 2025. In one test, 35 people aged 40 to 70, including some with sensitive skin, used the serum for 112 days. The brand reports wrinkles down 31%, luminosity up 53%, evenness up 42% and firmness up 13%. A second test of 35 women used an AI algorithm to estimate that skin looked about three years younger after four months. The brand also cites a Raman spectroscopy measurement of how deep the vitamin C reached and lab tests on skin samples exposed to UVA. None of these appear to have a comparison group or peer-reviewed publication, so they are best read as manufacturer claims.

For Indian buyers, the older Flavo-C serum is listed by at least one Indian beauty retailer, but we could not find an Indian listing for the Intense version at the time of writing.