Objective:To investigate differences in gut microbiota between patients with chronic spontaneous urticaria (CSU) and healthy controls.Methods:A total of 18 patients with CSU (CSU group) and 18 age- and gender-matched healthy controls (HC group) were enrolled from Department of Dermatology, Tianjin First Central Hospital between January 2019 and December 2019. Fecal samples were collected from these subjects, and total DNA was extracted. The 16S rRNA sequencing technology was used to identify microbial species in gut microbiota, and bioinformatics methods were applied to analyze differences in gut microbiota composition between the 2 groups. The SPSS 23.0 software was used for statistical analysis of the experimental data.Results:In terms of α diversity, there was no significant difference in the Observed OTU index, Chao1 index, Shannon index or Simpson index between the CSU group (161.28 ± 35.47, 161.31 ± 35.51, 5.15 ± 0.47, 0.94 ± 0.03, respectively) and HC group (154.89 ± 54.46, 154.92 ± 54.43, 4.92 ± 0.88, 0.91 ± 0.08, respectively; t = 0.417, 0.417, 0.952, 1.116, respectively, all P > 0.05) . In terms of β diversity, principal component analysis showed that the first and second principal components explained 6.66% and 4.93% respectively, and there was no significant difference in the microbiota structure between the 2 groups ( P = 0.672) . The relative abundance of the genus Holdemania in the gut microbiota significantly differed between the CSU group and HC group (0.04% vs. 0.01%, P = 0.025) . Conclusion:The gut microbiota differs between the patients with CSU and healthy controls.