Cowhage-induced itch is associated with neuroticism in patients with atopic dermatitis

Abstract

Background: There are different ways to induce itch in laboratory settings, e.g. the presentation of itch-related audiovisual stimuli or the application of pruritogens like cowhage. Itch, induced by audiovisual stimuli, is significantly related to depression and self-consciousness in patients with chronic itch. This study is the first to investigate whether also cowhage-induced itch is related to psychological variables in patients with chronic itch. Methods: 40 patients with atopic dermatitis (AD; 31 female) were shown two non-itch inducing videos lasting 10 minutes each. Immediately before the second video presentation, cowhage was applied to the forearm of the patients and not removed until the second video was over. Immediately after each video, patients rated their maximal itch intensity during the last video presentation. Increase of maximal itch due to cowhage was determined and correlated with personality factors, depression- and anxiety-scores. Findings: The application of cowhage led to a significant increase of maximal itch intensity in AD-patients [p < 0.001]. Induced itch was significantly positively related to neuroticism [p < 0.001; r = 0.544], which means that 29.6 % of the variance of induced itch could be explained by this factor. Discussion: This study showed that AD-patients, who report to be rather emotionally instable, vulnerable to stress, insecure and lack confidence, are more prone to experience itch due to cowhage than patients with the opposite psychological phenotype. Therefore, psychological interventions aiming to improve the patients` assertiveness and self-confidence might also help to improve their itch.