Topical formulations containing Zinc Oxide nanoparticles: Characterization and skin penetration

Zinc oxide is listed as “generally recognized as safe” material by the FDA. In 2016, the EU Cosmetics Regulation established that the zinc oxide nanoparticles (ZOn) are safe to be used as UV filter; however, more studies need to be developed to evaluate the safety of the cosmetic formulations. Thus, the aim of this study was to develop and characterize topical formulations containing 20% of coated (C) and non coated (NC) ZOn and assess the skin penetration using Reflectance Confocal Microscopy (RCM). The work of shear of formulations with NC and C were lower than the vehicle. Firmness, cohesiveness, consistency, and index of viscosity for formulations with NC and C were higher than for the vehicle. According to image analyses obtained from RCM, NC did not show major accumulation on the skin furrows (B1), while C (A2) and NC (B2) accumulated around the hair and in the hair follicles.