Central centrifugal cicatricial alopecia severity is associated with cowhage-induced itch

Summary Background Patients with central centrifugal cicatricial alopecia (CCCA) often suffer from varying degrees of itch, pain and burning sensations. However, the neural component of these skin sensations has not been assessed. Objective To conduct a comprehensive analysis of C nerve fibre function relating to itch and pain perception in patients with CCCA using thermosensory testing and experimental itch models. Methods Fifteen healthy African‐American women and 16 African‐American female patients with CCCA participated in the study and underwent quantitative computerized thermosensory testing to assess warmth and heat pain thresholds. Itch was induced using histamine iontophoresis and application of cowhage spicules, and the intensity of each itch was assessed. The association between itch intensity and CCCA severity score was examined. Results A positive correlation between CCCA severity score and peak itch ratings of cowhage on the lesional scalp (crown) was observed (P = 0·023, r = 0·562). Notably, the histamine peak itch rating was not found to have a significant correlation with CCCA severity score (P = 0·913). The crown also had significantly higher warmth and pain thresholds than the occiput in both healthy subjects and patients with CCCA. Conclusions Our results suggest a putative role for the protease‐activated receptor (PAR)‐2, which is activated by cowhage, in the pathogenesis of CCCA. Future studies should examine PAR‐2‐directed therapeutics for patients with CCCA. Examining for itch and other dysaesthesias in patients with CCCA is of vital importance to dermatologists in assessing disease severity. What’s already known about this topic? • Patients with central centrifugal cicatricial alopecia (CCCA) often complain of intense itch, pain and burning sensations. However, the neural component of these skin sensations has not been assessed. What does this study add? • This study demonstrates a significant correlation between cowhage‐induced itch intensity and the severity of CCCA. • As cowhage signals through the protease‐activated receptor (PAR)‐2, these results suggest a putative role for the PAR‐2 pathway in CCCA‐associated skin sensation. Examining for itch and other dysaesthesias in patients with CCCA is of vital importance to dermatologists in assessing disease severity.