Skin Hydration Potential of a Fluid Gel-Based Formulation of Kappaphycus alvarezii (Rhodophyta, Gigartinales)

The red alga Kappaphycus alvarezii is a rich source of bioactive compounds with potential applications in the cosmetic industry. This study aimed to characterize a cosmetic serum containing K. alvarezii and evaluate its immediate moisturizing effect on the skin. A randomized, triple-blind, parallel-group clinical trial was conducted with 28 healthy participants, allocated 1:1 to receive either a control formulation with hyaluronic acid or a test formulation with K. alvarezii. The formulations were assessed for stability over 60 days using organoleptic, microbiological, pH, and rheological analyses. Mechanical and bioadhesive properties were assessed using a texture analyzer, while the water content of the stratum corneum on the palms and backs of the hands was measured in vivo using a Corneometer® CM 825 (Courage & Khazaka Electronic GmbH). Both formulations showed similar stability and rheological behavior. Texture analysis indicated comparable compressibility and elasticity, with a slight reduction in bioadhesive strength for the test formulation. In vivo results demonstrated a moisturizing effect for both formulations, with a significant increase in palmar hydration 60 min after application of the K. alvarezii serum. These findings indicate that the formulation containing K. alvarezii can improve short term skin surface hydration; potential contributions of film formation and barrier modulation remain hypothetical and were not directly assessed in this study.