Since the 1960 s, our health has been compromised by exposure to over 350,000 newly introduced toxic substances, contributing to the current pandemic in allergic, autoimmune and metabolic diseases. The "Epithelial Barrier Theory" postulates that these diseases are exacerbated by persistent periepithelial inflammation (epithelitis) triggered by exposure to a wide range of epithelial barrier-damaging substances as well as genetic susceptibility. The epithelial barrier serves as the body's primary physical, chemical, and immunological barrier against external stimuli. A leaky epithelial barrier facilitates the translocation of the microbiome from the surface of the afflicted tissues to interepithelial and even deeper subepithelial locations. In turn, opportunistic bacterial colonization, microbiota dysbiosis, local inflammation and impaired tissue regeneration and remodelling follow. Migration of inflammatory cells to susceptible tissues contributes to damage and inflammation, initiating and aggravating many chronic inflammatory diseases. The objective of this review is to highlight and evaluate recent studies on epithelial physiology and its role in the pathogenesis of chronic diseases in light of the epithelial barrier theory.

自 20 世纪 60 年代以来，我们的健康因接触超过 350,000 种新引入的有毒物质而受到损害，导致当前过敏性疾病、自身免疫性疾病和代谢性疾病的流行。“上皮屏障理论”假设，这些疾病因暴露于多种上皮屏障破坏物质以及遗传易感性而引发的持续上皮周炎症（上皮炎）而加剧。上皮屏障是人体抵御外部刺激的主要物理、化学和免疫屏障。渗漏的上皮屏障有利于微生物组从受影响组织的表面转移到上皮间甚至更深的上皮下位置。反过来，机会性细菌定植、微生物群失调、局部炎症以及组织再生和重塑受损。炎症细胞迁移到易感组织会导致损伤和炎症，引发和加重许多慢性炎症性疾病。本综述的目的是根据上皮屏障理论，重点介绍和评估上皮生理学及其在慢性疾病发病机制中的作用的最新研究。