ABSTRACT
It is a common experience that the itch sensation can be reduced by the pain induced by scratching. Moreover, the itch sensation is intimately linked to the desire to scratch, which has recently been visualized as an activation of the premotor cortical areas in positron emission tomography investigations (13). The inhibition of itch by painful stimuli has been shown experimentally using various painful thermal, mechanical, and chemical stimuli. Recently, also electrical stimulation via an array of pointed electrodes, "cutaneous field stimulation," has been successfully used to inhibit itch for several hours in an area of more than 10 cm around the stimulated site suggesting a central mode of action (4). In line with these results, itch is suppressed inside the secondary zone of capsaicin-induced mechanical hyperalgesia (5). This central effect of capsaicin should be clearly separated from the neurotoxic effect it exerts locally on the nerve fibers (6), with both mechanisms inhibiting itch.
