Despite widespread use of silicon dioxide ($SiO_2$) NPs in industry and in our daily lives, no studies so far have evaluated the potential of their skin phototoxicity and sensitization. This study was designed to investigate the potential of phototoxicity and sensitization of $SiO_2$ NPs. Assessment of the potential of skin phototoxicity was carried out using the 3T3 neutral red uptake test, an HSEM, and an animal model. The potential of skin sensitization was evaluated by a non-radioisotope local lymph node assay (non-RI LLNA). Findings from the present study suggest that the HSEM may be a reasonable model system for evaluation of skin phototoxicity of NPs. In addition, our data demonstrate that non-RI LLNA may be a useful method for identification of skin sensitization of NPs. In this study, we showed that $SiO_2$ NPs do not induce phototoxicity or skin sensitization.