Recent progress in unraveling central nervous system processing of itch sensation.

Itch is the major symptom of many allergic or inflammatory skin diseases, yet it is still difficult to measure objectively. This article shows and updates the development and approaches of central nervous system investigation of itch.Human neuroimaging studies on the physiology and pathophysiology of itch sensation have been hampered by the lack of a reproducible "on-off" stimulus. Short-term alternating temperature modulation of histamine-induced itch has recently been shown to provide on-off characteristics.Recent studies with functional magnetic resonance imaging demonstrate that itch sensation in healthy volunteers is processed by a network of brain regions contributing to the encoding of sensory, emotional, attentional, evaluative, and motivational aspects of itch.