Expectations influence induced scratching behavior in patients with atopic dermatitis and healthy controls

Background: Itch and scratching can be induced by itch-related audiovisual stimuli. This study investigates whether expectations towards itch stimuli influence induced itch and scratching in patients with atopic dermatitis (AD) and healthy controls (HC). Methods: 40 AD-patients and 40 HC were randomized to an ‘informed’ (IG) or ‘uninformed’ group (UG). They were shown an itch-inducing experimental video (EV) and a control video (CV). The IG was told that the videos induce itch in many persons, the UG was not. Scratching during the video presentations was evaluated by two persons. Findings: Compared to the CV, the EV induced itch and scratching (p ≤ 0.01). IG and UG did not differ in induced itch intensity (p > 0.05). Concerning induced scratching, the UG showed a higher increase in the number of scratch movements (p = 0.001) and scratch duration (p < 0.001) compared to the IG. Discussion: The results indicate that being ‘warned’ about itch stimuli increases the possibility to prevent scratching. Next, informed AD-patients and HC should be compared regarding their capability to prevent themselves from scratching.