Chronic Urticaria and Gut Microbiome

Recent studies have linked gut microorganism composition and chronic urticaria; however, the underlying mechanisms responsible for this connection are unknown. Since the human immune system is in homeostasis with microbiota, and the composition of the microbiome regulates the development and function of the immune system, it is likely that an alteration of microbiota components (dysbiosis) could influence the course of chronic spontaneous urticaria, including disease severity, patient quality of life and treatment outcome. To date, several studies have identified changes in the gut microbiota composition of patients with chronic spontaneous urticaria, though only a few have exhibited metabolic abnormalities associated with gut dysbiosis. The studies on chronic spontaneous urticaria patients predominantly showed that the relative abundance of beneficial bacteria was decreased (Firmicutes and Bacteroides), while that of opportunistic bacteria was increased (Enterobacteria and Proteobacteria). These findings are potentially associated with inflammation mediated by the imbalance of Th1/Th2/Th17 cytokines, which might contribute to chronic spontaneous urticaria pathogenesis.