Understanding neural mechanisms of mechanical itch.

Chronic itch, which is associated with many skin disorders and systemic diseases, is often difficult to treat and can greatly affect quality of life. Patients with chronic itch commonly have both peripheral and central sensitization of itch signaling pathways, which enables pruritogens to elicit an exaggerated itch response (known as chemical itch) and allows innocuous mechanical stimuli to evoke itch sensation (known as mechanical itch), resulting in persistent and ongoing itch. Fully understanding the mechanism of itch sensitization is critical for designing success-ful therapeutic strategies to treat chronic itch. In recent years, significant progress has been made in identifying the molecular, cellular, and circuit mechanisms underlying chemical itch.1 How-ever, understanding the pathways and mechanisms of mechanical itch associated with both acute and chronic itch is still in its early stages.