The present invention relates to topical compositions containing a dispersion of composite particles. Each of such composite particles contains one or more core particles encapsulated or entrapped in a polymeric shell. At least some of the core particles are formed of a material capable of causing generation of reactive oxygen species (ROS). Each of the composite particles further contains: (1) a first antioxidant co-encapsulated or co-entrapped with the core particles inside the polymeric shell for quenching or scavenging ROS generated in the vicinity of the core particles, and (2) a second antioxidant coated over the polymeric shell for preventing or reducing oxidative damage to the skin, such as lipid peroxidation. The particle dispersion of the present invention therefore can be readily formulated into topical sunscreen compositions with organic sunscreen agents susceptible to oxidative decomposition or degradation to provide improved protection against skin damage caused by exposure to UV light.