Author(s): Astrid Stumpf 1,*, Markus Burgmer 1, Gudrun Schneider 1, Gereon Heuft 1, Martin Schmelz 4, Ngoc Quan Phan 3, Sonja Ständer 3, Bettina Pfleiderer 2
Itch is a very common symptom of many dermatological diseases. Especially chronic itch reduces quality of life and might lead to depression and anxiety symptomatology -. Sex and gender are increasingly perceived as important factors influencing the extent of symptomatology, treatment response and outcome -.
Still there is only very little knowledge about sex and gender differences in chronic pruritus. Ständer et al.  examined a large sample of patients with chronic pruritus. In this study, females reported higher itch intensities and were more negatively affected by pruritus. In line with that Holm et al.  found that women were more affected by visible areas of atopic dermatitis than men. Uttjek et al.  could show that women suffering from psoriasis had different expectations related to dermatological care than male patients.
During the last years, similarities and interactions in acute transmission and sensitization processes between itch and pain were described -. In imaging studies of pain, women presented a higher activity in prefrontal, somatosensory and parietal gyri as well as in insula, dorsolateral prefrontal cortex (DLPFC), cingulate cortex, para-/hippocampus, cerebellum and thalamus even when the maximal pain intensity ratings were comparable between women and men -.
Cognitive attention or distraction has a major influence on pain or itch perception. Distraction as a cognitive factor shifting the subject's attention away from clinical pain or itch can reduce itch and pain intensity -. Keogh at al.  reported that men were more easily distractible than women from experienced pain. In another study examining the effect of smoking and distraction on pain sensitivity, men had less pain during distraction . However, in a distraction study using local analgesia for oro-dental injections there was no sex difference in pain reduction .
To our knowledge, there is no paper published in the current literature on sex differences in central itch perception and impact of distraction on brain activity. Based on previous results in pain research and since it was discussed that pain and itch processing are comparable  we hypothesized that on the psychophysical level females will present higher itch intensities and desire to scratch that will decrease during distraction. In BOLD fMRI, females will show up-regulated activities of prefrontal, somatosensory and parietal gyri as well as in the insula, dorsolateral prefrontal cortex (DLPFC), cingulate cortex, para-/hippocampus, cerebellum and thalamus in response to itch when compared to men. Moreover, we assume that distraction will result in a more pronounced itch intensity reduction in men as compared to women.
33 healthy subjects without history of chronic disease, allergy or mental illness were included in the study (17 women, mean ± SD age 24.3±2.8 years, 16 men, mean ± SD age 26.8±4.1 years). 28 participants were right handed, 5 left handed (3 women). All subjects provided written informed consent. The study was approved by the local Ethics Committee of...