Historical Background -- Epidemiology of the Burden of Chronic Itch -- Neurophysiology and Itch Pathways -- Brain Mechanisms of Chronic Itch -- Mouse and Human Models of Itch. Transient Receptor Potential Channels and Itch -- Cytokines and Itch -- Role of Mrgpr Family of Receptors and Itch -- Protease-activated Receptor Agonists and Itch -- VGLUT2-dependent Sensory Neurons and Itch -- Identification and Characterization of Spinal Inhibitory Neurons That Inhibit Itch -- Noradrenergic Itch Transmission in the Spinal Cord -- NK-1 Antagonists and Itch -- Cannabinoids and Itch -- Antihistamines and Itch -- Targeting Itch with Ligands Selective for k Opioid Receptors -- Neuraxial Opioid-induced Scratching and Its Pharmacological Antagonism -- Topical Therapies -- Allergic Itch in Dogs.