“…Histamine, a biogenic amine with multiple physiological effects, exerts its biological activities through four distinct G-protein-coupled receptors (GPCRs) known as the histamine H1, H2, H3, and H4 receptors [1] , [2] . The histamine H1 and H2 receptors were identified decades ago [3] , [4] , and have been shown to be excellent drug targets for the treatment of allergy and gastric ulcers, respectively [5] , [6] . The histamine H4 receptor was discovered in 2000 [7] , and it has been identified as a potential target for the treatment of inflammatory diseases such as chronic allergies, asthma, atopic dermatitis, and inflammatory bowel diseases [8] .…”