This letter is intended to clarify the clinical effectiveness of neuropeptide substance P (SP) in reducing age-related skin wrinkling. This is the first clinical study to evaluate the efficacy of the topical application of SP on wrinkle reduction. For the clinical study, we tested the efficacy of a stable SP formulation known as SP-based hydrogel against skin aging in study participants. We found that this SP-based hydrogel reduced skin aging based on changes observed in several cutaneous parameters.
