Substance P and the itch-scratch response

Substance P (SP), a neuropeptide diffusely scattered in the nervous system and immune system, participates in various physiological and pathological processes, including pain perception and inflammatory response. However, the regulatory mechanisms of SP in itch perception and its downstream pathophysiological responses, such as the chronic itch-scratch vicious cycle, have not been systematically elucidated. Based on an analysis of the existing literature, this review summarizes the biological functions of substance P in the itch-scratch response, and explores its mechanism of action in signal transduction, inflammatory response and nerve sensitization.