Itch Perception and Skin Reactions as Modulated by Verbal Suggestions: Role of Participant's and Investigator's Sex.

This study investigated sex-specific differences in itch perception and skin reactions, as modulated by verbal suggestions, and the role of the investigator's sex. Healthy volunteers (50 males, 50 females), divided into 4 groups, were tested by male and female investigators. Itch was induced via prick testing with sodium chloride and histamine in 4 runs; 2 control conditions (with no exaggerated verbal comments about expected itch) and 2 experimental conditions (with exaggerated verbal comments). After 5 min, wheal and flare reactions were measured and itch intensity was rated by subjects on a numerical rating scale. Exaggerated verbal suggestions resulted in higher itch intensity ratings in the sodium chloride and histamine condition, and higher unpleasantness ratings and a wheal of greater extent in the sodium chloride condition, as well as a flare of greater extent in the histamine condition. The magnitude of the differences between the exaggerated verbal suggestion conditions and respective control conditions was only significantly different between male and female investigators concerning flare size in the histamine condition. There were no differences between male and female participants. Therefore, sex differences may play only a minor role in nocebo-induced itch perception.