Formulation and Evaluation of Rice Washed Water-Based Gel for Enhancing Skin Hydration

Abstract

Introduction: Rice washing water (RWW) contains bioactive compounds such as vitamins, amino acids, and antioxidants that contribute to skin hydration. Despite its potential, limited studies have examined its stability and compatibility in topical gel formulations. Carbomer 940 is a commonly used gelling agent that influences viscosity, spreadability, and overall gel performance. Aims: The present study sought to systematically evaluate the effect of varying concentrations of RWW (5%, 10%, and 15%) within Carbomer-based gels (1% and 2%), with emphasis on physicochemical stability, safety, and moisturizing efficacy. Result: Six gel formulations (F1–F6) and two bases (FA and FB) were evaluated for organoleptic properties, pH, viscosity, spreadability, adhesion, homogeneity, irritation, and skin hydration on 20 volunteers with dry skin (18–40 years) using a digital skin analyzer. All formulations exhibited stable pH values (4.4–6.4) and maintained homogeneity throughout 28 days of storage. Viscosity increased with higher Carbomer concentration, while spreadability decreased accordingly. Adhesion values (1.5–4.5 seconds) and irritation index (≤0.4) indicated acceptable safety and usability. Statistical analysis showed that rice washing water at concentrations of 10–15% in the 1% Carbomer base provided the most effective balance of viscosity, spreadability, and moisturizing effect, with significant improvements in skin hydration (p<0.05).  Conclusion: Rice washing water gel formulations demonstrated good physicochemical stability, safety, and significant moisturizing effects. The most promising results were observed in gels containing 10–15% rice washing water with a 1% Carbomer base, supporting its potential application as a natural hydrating cosmetic ingredient.