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Background Sensitive skin is a subjective cutaneous hyper‐reactivity that occurs in response to various innocuous stimuli. Keratinocytes have recently been shown to participate in sensory transduction by releasing many neuroactive molecules that bind to intra‐epidermal free nerve endings and modulate nociception. In the literature, the characterization of these interactions has been based on the co‐culture of keratinocyte and mammalian‐origin neuronal cell lines. In this study, we established an in vitro model based on a co‐culture of primary human keratinocytes and differentiated SH‐SY5Y cells, a human neuronal cell line. Methods Human epidermal keratinocytes and SH‐SY5Y cells were monocultured and co‐cultured. Changes in calcium influx, substance P, inflammatory cytokines, and neuropeptides between the monoculture and co‐culture groups treated with capsaicin only and capsaicin with transient receptor potential channel vanilloid subfamily member 1 (TRPV1) antagonist, trans‐4‐tert‐butylcyclohexanol (TTBC), together. In addition, the difference in stinging sensation was evaluated by applying it to the volunteers. Results When SH‐SY5Y cells were co‐cultured with keratinocytes, they had no significant effect on axonal development. Substance P was also released after capsaicin treatment and reduced by TTBC under co‐culture conditions. Moreover, the expression of inflammatory cytokines and neuropeptides was significantly increased in co‐cultured keratinocytes compared to that under monoculture conditions. In addition, the stinging sensation was significantly induced after the application of capsaicin in vivo and was relieved after the application of the TRPV1 antagonist. Conclusion We demonstrated that the novel co‐culture model is functionally valid through capsaicin and TRPV1 antagonist. We also confirmed that TTBC could be used for the treatment of sensitive skin through a co‐culture model and in vivo tests. This co‐culture model of keratinocytes and SH‐SY5Y cells may be useful in vitro alternatives for studying the close communication between keratinocytes and neuronal cells and for screening therapeutic drugs for sensitive skin.

Background: Some alopecic diseases can be diagnosed by detailed history taking and physical examination, but in many cases, biopsy must be performed to make a definite diagnosis. Aims and Objectives: This study aimed to evaluate the clinico-pathological concordance of scalp lesions showing alopecia. Materials and Methods: We retrospectively reviewed the electronic medical records and biopsy slides of patients who underwent biopsy for evaluating scalp lesions showing alopecia. Based on the definitions of clinico-pathological concordances, scalp alopecic disease was evaluated. Results: A total of 121 patients were enrolled in the study. A total of 203 clinical differential diagnoses were made before performing a biopsy. Thirty-one patients showed full concordance, and 58 patients showed partial concordance; thus overall concordance was shown in 89 patients (73.55%). Folliculitis decalvans and alopecia areata showed a higher full concordance rate than average (P < 0.05), whereas dissecting folliculitis showed a lower overall concordance rate than average, and folliculitis decalvans showed a higher overall concordance rate than average (P < 0.05). The overall concordance rate of alopecia areata was 100% (P = 0.061). Conclusion: In diagnosing folliculitis decalvans and alopecia areata, which showed high full and overall concordance, performing a biopsy to make a definite diagnosis is not always necessary, especially when patients show typical clinical features. Dissecting folliculitis, which showed low overall concordance, was less likely to be suspected as a clinical differential diagnosis, making it difficult to distinguish based on clinical findings alone. Therefore, when it is suspected, a detailed evaluation including a biopsy is recommended.