The topical application of nanomedicines is still a topic of much debate, regarding their real benefit over more traditional formulations, their specific mechanism of action in the skin and the safety of potentially biopersistent nanomaterials and their by-products within the skin layers . In the present study, we aimed to evaluate if the in vitro accumulation of clobetasol-17-propionate evidenced with the NP formulation would improve the efficacy in vivo. Furthermore, the skin tolerability of the formulation was investigated and the possible drug release mechanism of the nanoparticles discussed, with the aim to rule out that tissue structure modifications could be the cause of the enhanced efficacy shown when using the nanoformulation.