Abstract:Specially designed transcutaneous electrical stimulation paradigms can be used to provoke experimental itch. However, it is unclear which primary afferent fibers are activated and whether they represent pathophysiologically relevant, C-fiber mediated itch. Since low-threshold mechano-receptors have recently been implicated in pruriception we aimed to characterize the peripheral primary afferent subpopulation conveying electrically evoked itch in humans (50Hz stimulation, 100μs square pulses, stimulus-response … Show more
Itch is a commonly experienced symptom of acute and chronic dermatological and systemic conditions. Placebo and nocebo effects, positive and negative effects experienced after both real and sham interventions, putatively due to positive or negative outcome expectancies, can have a significant impact on the experience of itch and its treatment. Experimental methods to induce and study placebo and nocebo effects on itch have been developed, utilizing various combinations of expectancy-induction methods (eg, conditioning, verbal suggestions) and short-acting itch-evoking stimuli (eg, histamine, electrical, or mechanical stimulation). The aim of this review is to describe the current research methods used to induce placebo and nocebo effects on itch, and the results of these studies. The benefits and drawbacks of different expectancy-induction methods and itch-evoking stimuli are described, and future directions for research and clinical application are discussed.
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