FORMULATION OPTIMIZATION OF SKIN REPAIRING AND HYDRATING FACIAL CLEANSING STICK USING RESPONSE SURFACE METHODOLOGY

The present study was carried out to optimize a skin-repairing and hydrating facial cleansing stick containing Centella asiatica leaves extract using Response Surface Methodology (RSM). Glycerin and sodium cocoyl isethionate (SCI) were selected as independent formulation variables due to their major influence on hydration and cleansing performance. A Design of Experiments (DOE) approach was employed to study the combined effect of glycerin (15–25) and SCI (20–40) on spreadability and foamability, which were selected as critical response parameters. Experimental data were analyzed using response surface and contour plots to understand the effect of formulation variables on the selected responses. The results showed that glycerin had a positive influence on spreadability, while increasing SCI improved foamability but reduced spreadability at higher levels. Numerical optimization based on the desirability function identified an optimized formulation containing 25 glycerin and 20 SCI, which provided a balanced response for both spreadability and foamability. The study demonstrates that RSM is an effective tool for optimizing facial cleansing stick formulations containing Centella asiatica leaves extract.