Reducing Zinc Oxide Toxicity via Surface Modification: Emerging Strategies for Cosmetic Applications

ZnO is widely used in environmental, energy, and human-health-related applications, particularly in cosmetics as a white pigment and UV filter, with a maximum allowable concentration of 25%. However, nanoscale ZnO at high concentrations may pose potential toxicity risks, even for topical use. This study summarizes recent biological findings related to ZnO, emphasizing its ability to generate reactive oxygen species under both light and dark conditions, although at different levels. Such activity raises concerns regarding oxidative stress and potential cellular damage. To mitigate these risks, various surface modification strategies have been developed to improve the safety and stability of ZnO. These include inorganic coatings (e.g. SiO2) that suppress photocatalytic activity and reduce free radical formation; organic coatings using fatty acids, biopolymers, or peptides to enhance stability and biocompatibility; hybrid inorganic–organic systems (e.g. organosilanes) that combine the advantages of both approaches; and nanocomposite strategies integrating ZnO into polymer matrices to improve dispersion, stability, and functionality. Overall, these approaches provide valuable insights and practical directions for optimizing the safety and performance of ZnO in cosmetic applications.