Evaluation of skin penetration and sun protection factors of sunscreen products

Abstract

Evaluation of skin penetration and sun protection factors of sunscreen products were studied. Two type of emulsions; oil in water and water in oil were used to evaluate. Both type of emulsions were the most commonly used. In this study the sunscreen emulsions were formulated by varying the concentration of various type of sunscreen agents. The emulsions were improved by incorporating the water resistant agent, 3% W/W silicone oil 350 cps, into the emulsions. All of preparation was stable, the pH was in the range of 7.0 +_ 0.5 and spread homogenously. The in vitro SPF method was determined by using SPF-290s analyzer. Results indicated that the effectiveness of the sunscreen products were depended on concentration of sunscreen agents and independed on the type of emulsion. The water resistant agent (silicone oil viscosity 350 cps) could not significantly improve the SPF of sunscreen emulsions. The in vitro skin penetration through human skin was measured by using modified franz diffusion cell apparatus. Most of sunscreen agents was localized at stratum corneum; they could not pass into the receptor fluid. The in vivo SPF method, US-FDA method, the SPF of standard homosalate was found to be well with in the requirement of SPF 4.0, but the formulation of various concentration of sunscreen agents showed lower SPF value than the in vitro method using SPF-290s analyzer. The in vitro SPF showed low correlation with the in vivo SPF data obtained by the US-FDA method with correlation coefficient (r) = 0.5658.