Microbial dysbiosis in the skin has been implicated in the pathogenesis of atopic dermatitis (AD); however, whether and how changes in the skin microbiome initiate skin inflammation, or vice versa, remains poorly understood. Here, we report that the levels of sebum and its microbial metabolite, propionate, were lower on the skin surface of AD patients compared with those of healthy individuals. Topical propionate application attenuated skin inflammation in mice with MC903-induced AD-like dermatitis by inhibiting IL-33 production in keratinocytes, an effect that was mediated through inhibition of HDAC and regulation of the AhR signaling pathway. Mice lacking sebum spontaneously developed AD-like dermatitis, which was improved by topical propionate application. A proof-of-concept clinical study further demonstrated the beneficial therapeutic effects of topical propionate application in AD patients. In summary, we have uncovered that the dysregulated sebum–microbial metabolite–IL-33 axis might play an initiating role in AD-related skin inflammation, thereby highlighting novel therapeutic strategies for the treatment of AD.

Atopic dermatitis (AD) is now a global health problem and has been attracting extensive attention from both academic and public society in China. This review aimed to present the current status of the prevalence, disease burden, clinical features, diagnosis, and management of AD in China. The prevalence of AD has been increasing rapidly in China during the past decades, partially due to the increased recognition of the disease; there are still substantial amounts of over-diagnosed eczema and under-diagnosed AD. Chinese dermatologists see many AD patients with atypical manifestation, which poses a challenge to the diagnosis. The Chinese diagnostic criteria for adults and pediatric patients with AD have been proposed respectively and validated with high sensitivity and specificity. International and Chinese guidelines for management of AD have been popularized; however, there are still many practices that need verification through randomized case-control study. Dupilumab and JAK inhibitors have demonstrated favorable efficacy for AD patients in China, and a multidimensional approach is needed for selection of the patients and evaluation of the efficacy and safety. Patient education and long-term management for AD are just beginning in China, and need to be strengthened in the future.

Background/Objective: Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by diverse clinical manifestations. However, variations in its clinical presentations across different ages, genders, anatomical sites, and seasons remain incompletely understood. The objective was to explore the clinical heterogeneities of AD using data from the Chinese non-selective registration system. Methods: A prospective analysis was conducted on 3829 AD patients enrolled in the Chinese Non-selective Registry for AD (CNRAD) at hospital settings from 2020 to 2022. Demographic profiles; distribution, type, and severity of the skin lesion; laboratory findings; allergic comorbidities; family history; and exacerbating factors were analyzed. Results: The male-to-female ratio was 0.92 among adolescent and adult AD patients but increased to 2.11 in elderly AD patients, highlighting an age-dependent gender difference in AD prevalence. Age groups displayed distinct anatomical preferences for lesion distribution, with reduced involvement of the cubital and popliteal fossae in adult and elderly patients. Based on skin lesion characteristics, ten clinical subtypes of AD were proposed. Elderly AD patients exhibited higher severity, compared to adolescence and adult AD patients, with male patients being more severe than females. Elderly AD patients showed a lower proportion of extrinsic type, compared to childhood AD patients. Seasonal change emerged as the most important factor triggering AD flares. Conclusions: This study provides new insights into the heterogeneities of AD clinical manifestations in the Chinese population, demonstrating their significant dependence on temporal factors, including age and season.