Influence of topical capsaicin on facial sensitivity in response to experimental pain

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Abstract
summary Capsaicin, the pungent component of the red pepper, has been used as an analgesic in a variety of pain conditions, but sensory impairment after long‐term treatment has been concerned. This study investigated the influence of topical capsaicin on various types of sensations including pain in the facial areas innervated by the mental nerve, and also evaluated whether the measurement of cutaneous current perception threshold (CPT) is reliable for the quantification of sensory change following capsaicin application. Twenty healthy subjects were given topical capsaicin cream (0·075%), which was applied to the mental area unilaterally, four times daily for 2 weeks. Burning sensation after capsaicin application gradually decreased with repeated applications. Repeated topical capsaicin resulted in reduced sensation to mechanical, heat and cold pain without changing non‐painful tactile sensation. It also resulted in increased CPTs at 5 Hz and 250 Hz stimuli but no change in the CPTs at 2000 Hz from the first evaluation after capsaicin treatment and throughout the treatment period. This study demonstrated that topical capsaicin treatment for the management of chronic localized pain can be safely applied to the face without affecting non‐painful normal sensations, and that CPT testing is a clinically useful tool for the quantification of sensory changes following capsaicin application.