Objective To study and compare the oral microbiota and metabolites of children with Henoch Schonlein purpura(HSP)to identify specific microbiota and metabolites related to this disease and elucidate the pathogenesis of HSP.Methods Three groups of qualified subjects were included,including 20 in the HSP group,20 in the HSP nephritis(HSPN)group,and 20 in the control group.Perform high-throughput 16S rRNA sequencing and metabolic profiling of saliva from each group to analyze the correlation between differential microbiota and differ-ential metabolites.Results(1)Compared with the control group,there was a significant difference in richness and diversity in the HSPN group(P＜0.05).At the same time,there was no significant difference in richness and diver-sity in the HSP group(P＞0.05).Compared with the HSP group,the abundance,and diversity of the HSPN group were significantly increased(P＜0.05).At the genus level,the proportion of Streptococcus in each group is the high-est.Compared with the control group,there was no significant correlation between the HSP group and the genus of bacteria.In contrast,the HSPN group showed a significant increase in the genera of Pseudomonas and Parabacteroi-des(P＜0.05).Compared with the HSP group,the abundance of Pseudomonas and Parabacteroides in the HSPN group was significantly increased(P＜0.05).(2)Compared with the control group,the HSPN group had 12 differen-tial metabolites involving nine metabolic pathways,such as phenylalanine metabolism;There was no significant dif-ference in metabolites and no metabolic pathway in the HSP group.Compared with the HSP group,the HSPN group has 15 differential metabolites involving nine metabolic pathways,such as phenylalanine metabolism.(3)In the HSPN and control groups,Pseudomonas and Parabacteroides negatively correlated with Phenylalanine metabolic pathway products.In the HSPN and HSP groups,Pseudomonas,Parabacteroides,and Phenylalanine metabolic path-way products were negatively correlated.The metabolites involved in phenylalanine metabolism in the oral cavity are 2-hydroxycinnamic acid,Phenylpyruvic acid,and N-acetyl-L-phenylalanine.Conclusion There is a significant dif-ference between HSPN and HSP children and healthy children.Streptococcus,Pseudomonas,and Parabacteroides may be one of the trigger factors of HSPN,and Phenylalanine metabolism may be one of the pathways in the patho-genesis of HSPN.Children with HSPN have a more pronounced imbalance in oral microbiota and greater differences in metabolic products than children with HSP.