[Placebo and nocebo effects on itch : Methodological and clinical implications].

Patients often experience positive (placebo) or negative (nocebo) treatment effects due to the positive or negative expectations they have about the treatment. Placebo and nocebo effects have only relatively recently received attention for itch. Experimental studies indicate that, in line with research in other areas, such as pain, learning via verbal suggestion and conditioning plays a key role in placebo and nocebo effects on itch. Results on contagious itch emphasize the role of observational learning and suggest that itch sensations might be particularly susceptible to suggestion and therefore placebo and nocebo effects. Substantial itch reductions in the placebo arms of clinical trials suggest that placebo effects are also important for clinical practice. In this article, an overview is given of how placebo and nocebo effects on itch can optimally be used in research and for the treatment of itch.