Smell and taste dissociations in the modulation of tonic pain perception induced by a capsaicin cream application

Background: Pain is a subjective experience characterized by sensory (intensity) and emotional (unpleasantness) aspects. Although literature reports behavioral effects on pain due to smell and taste influence, to our knowledge the relationship between tonic pain induced by a capsaicin cream and these chemosensory systems has never been explored before. The aim of this study was to investigate the modulation of olfactory and gustatory substances having different valence on tonic pain perception mediated by a capsaicin cream application. Methods: Sixty healthy volunteers were included in two separated experiments (N=30 smell; N=30 taste) and underwent different valence smell and taste stimulations, while receiving painful stimuli. Perception of pain intensity (the sensory component) and unpleasantness (the affective component) was measured with a numerical rating scale, both during the two aforementioned experiments. Results: Pain unpleasantness rating showed differences only in the smell experiment between the two odorous conditions. In particular, pleasant odor induced lower ratings of pain unpleasantness, while no significant results were found for intensity. Regarding taste, we couldn't observe significant effects nor for pain unpleasantness or intensity. Conclusions: These findings highlight the potential role of pleasant odors in influencing the affective aspects of pain perception induced by this kind of tonic pain. Such evidence might provide new insight for using chemosensory substances as analgesics for modulating the cognitive aspects of neuropathic pain.