Placebo and nocebo responses in itch clinically relevant responses?

Research on analgesic placebo and nocebo responses shows, that expectancy plays a key role in generating and maintaining these effects. Expectations are modulated via verbal instructions, conditioning and social learning processes. Recent studies also discussed the role of earlier learning experiences in placebo or nocebo responses as well as the role of personal factors like emotions and the whish and certainty on itch relief of patients. Nowadays, placebo and nocebo responses have been examined in relation with itch processes in the dermatology and especially in the field of allergology. But there are only a few studies, although the similarity of itch to pain has already been proofed. In this review the concept of placebo and nocebo responses, its main mechanisms and psychological factors is being discussed, as well as its clinical relevance for pruritus as a treatable symptom in dermatology and allergology.