IL31 and Alzheimer disease: Several itch mediators and their corresponding receptors are reported to be responsible for itch in AD: histamine (H), especially the role of H1 and H4 receptors (H1R and H4R) [157, 162], certain proteases (including tryptase, dust mites, and S. aureus [151]), substance P [63, 151], IL-31 [163, 164], TSLP [165], and endothelin-1 [166].