Abnormalities in Gut Microbiota and Metabolism in Patients With Chronic Spontaneous Urticaria

Association between gut microbiota and pan-dermatological diseases: a bidirectional Mendelian randomization research

Background

Gut microbiota has been associated with dermatological problems in earlier observational studies. However, it is unclear whether gut microbiota has a causal function in dermatological diseases.

Methods

Thirteen dermatological diseases were the subject of bidirectional Mendelian randomization (MR) research aimed at identifying potential causal links between gut microbiota and these diseases. Summary statistics for the Genome-Wide Association Study (GWAS) of gut microbiota and dermatological diseases were obtained from public datasets. With the goal of evaluating the causal estimates, five acknowledged MR approaches were utilized along with multiple testing corrections, with inverse variance weighted (IVW) regression serving as the main methodology. Regarding the taxa that were causally linked with dermatological diseases in the forward MR analysis, reverse MR was performed. A series of sensitivity analyses were conducted to test the robustness of the causal estimates.

Results

The combined results of the five MR methods and sensitivity analysis showed 94 suggestive and five significant causal relationships. In particular, the genus Eubacterium_fissicatena_group increased the risk of developing psoriasis vulgaris (odds ratio [OR] = 1.32, pFDR = 4.36 × 10-3), family Bacteroidaceae (OR = 2.25, pFDR = 4.39 × 10-3), genus Allisonella (OR = 1.42, pFDR = 1.29 × 10-2), and genus Bacteroides (OR = 2.25, pFDR = 1.29 × 10-2) increased the risk of developing acne; and the genus Intestinibacter increased the risk of urticaria (OR = 1.30, pFDR = 9.13 × 10-3). A reverse MR study revealed insufficient evidence for a significant causal relationship. In addition, there was no discernible horizontal pleiotropy or heterogeneity.

Conclusion

This study provides novel insights into the causality of gut microbiota in dermatological diseases and therapeutic or preventive paradigms for cutaneous conditions.

Current insights on gut microbiome and chronic urticaria: progress in the pathogenesis and opportunities for novel therapeutic approaches

Chronic urticaria (CU) is a prevalent skin disorder greatly impacting the patients' life quality, in which immune dysregulation mediated by gut microbiome plays a significant role. Several studies have found the gut dysbiosis exists in patients with CU. In addition, infection may also be one of the causes of CU. The primary treatment currently used for CU is the second-generation non-sedating H1-antihistamines (nsAH). However, there are some limitations in current therapies. Based on the latest evidence, this review provides an updated overview of how the gut dysbiosis influences CU development, explores potential therapeutic approaches based on the gut microbiota and summarizes the interaction between gut microbiota and current treatment.

The Role and Mechanism of Metformin in Inflammatory Diseases

Metformin is a classical drug used to treat type 2 diabetes. With the development of research on metformin, it has been found that metformin also has several advantages aside from its hypoglycemic effect, such as anti-inflammatory, anti-aging, anti-cancer, improving intestinal flora, and other effects. The prevention of inflammation is critical because chronic inflammation is associated with numerous diseases of considerable public health. Therefore, there has been growing interest in the role of metformin in treating various inflammatory conditions. However, the precise anti-inflammatory mechanisms of metformin were inconsistent in the reported studies. Thus, this review aims to summarize various currently known possible mechanisms of metformin involved in inflammatory diseases and provide references for the clinical application of metformin.

Research progress in the pathogenesis of chronic urticaria

Chronic urticaria is very common in clinic, but its pathogenesis is not fully elucidated. Most patients can't find the exact cause, resulting in misdiagnosis or delayed treatment. Previous studies have found that mast cell activation is the central link in the pathogenesis of chronic urticaria. Genetics, autoimmune, coagulation disorders, and infection may also be involved in the pathophysiological process of chronic urticaria. With the deepening of research, more immune and non-immune mechanisms have been gradually revealed in the pathogenesis of chronic urticaria, such as the interaction of immune cells in the microenvironment of urticaria, intestinal flora and metabolism, neuroimmunity, environmental factors and hormones. Clarifying the pathogenesis of chronic urticaria will help to find more treatment targets and provide more diversified ideas for clinical diagnosis and treatment.

Brain network mechanism of acupuncture for chronic spontaneous urticaria: a functional magnetic resonance imaging study protocol

Introduction

Chronic spontaneous urticaria (CSU) is a common skin condition that can significantly impact patients' quality of life. Although studies have demonstrated the efficacy of acupuncture in treating CSU, the underlying mechanisms remain unclear. Dysfunction within the brain's default mode network (DMN) represents a fundamental characteristic of central pathological changes associated with CSU. Therefore, it is hypothesized that improving brain network dysfunction could serve as a key mechanism through which acupuncture exerts its therapeutic effects. This study aims to provide evidence supporting this hypothesis.

Methods and analysis

This study, a parallel, randomized, sham-controlled functional neuroimaging investigation will be conducted in China. We aim to enroll 50 patients with CSU and 25 healthy controls, distributing them evenly between the acupuncture and sham acupuncture groups in a 1:1 ratio. The total observation period will span 6 weeks, including 2 weeks designated for the baseline phase and 4 weeks allocated for the clinical treatment phase. Prior to treatment, all participants will undergo magnetic resonance scanning, clinical index detection, and microbiota collection. Following treatment, the patients with CSU will be retested for these indicators. Using resting-state functional connectivity (rsFC) analysis, dynamic Functional Connection (dFC) analysis, and brain microstate extraction technology combined with correlation analysis of microbiota and clinical indicators, the regulatory mechanism of acupuncture on the brain network of CSU will be evaluated from multiple dimensions.

Ethics and dissemination

This trial was approved by the Biomedical Ethics Review Committee of the West China Hospital, Sichuan University (No. 2022-1255). Each participant will provide written informed consent to publish any potentially identifiable images or data.Clinical trial registrationhttps://www.chictr.org.cn/, identifier: ChiCTR2200064563.

Immune-mediated hematological disease in dogs is associated with alterations of the fecal microbiota: a pilot study

BACKGROUND

The dog is the most popular companion animal and is a valuable large animal model for several human diseases. Canine immune-mediated hematological diseases, including immune-mediated hemolytic anemia (IMHA) and immune thrombocytopenia (ITP), share many features in common with autoimmune hematological diseases of humans. The gut microbiome has been linked to systemic illness, but few studies have evaluated its association with immune-mediated hematological disease. To address this knowledge gap, 16S rRNA gene sequencing was used to profile the fecal microbiota of dogs with spontaneous IMHA and ITP at presentation and following successful treatment. In total, 21 affected and 13 healthy control dogs were included in the study.

RESULTS

IMHA/ITP is associated with remodeling of fecal microbiota, marked by decreased relative abundance of the spirochete Treponema spp., increased relative abundance of the pathobionts Clostridium septicum and Escherichia coli, and increased overall microbial diversity. Logistic regression analysis demonstrated that Treponema spp. were associated with decreased risk of IMHA/ITP (odds ratio [OR] 0.24-0.34), while Ruminococcaceae UCG-009 and Christensenellaceae R-7 group were associated with increased risk of disease (OR = 6.84 [95% CI 2-32.74] and 8.36 [95% CI 1.85-71.88] respectively).

CONCLUSIONS

This study demonstrates an association of immune-mediated hematological diseases in dogs with fecal dysbiosis, and points to specific bacterial genera as biomarkers of disease. Microbes identified as positive or negative risk factors for IMHA/ITP represent an area for future research as potential targets for new diagnostic assays and/or therapeutic applications.

Causal relationship between gut microbiota and urticaria: a bidirectional two-sample mendelian randomization study

Background

Cumulative evidence showed an association between gut microbiota and urticaria, but the causal relationship between them is unclear. We aimed to verify whether there is a causal relationship between the composition of gut microbiota and urticaria and explore whether the causal effect was bidirectional.

Methods

We obtained genome-wide association studies (GWAS) summary data of 211 gut microbiota and urticaria from the most extensive available GWAS database. A bidirectional two-sample mendelian randomization (MR) study was used to test the causal relationship between the gut microbiota and urticaria. The MR analysis was primarily performed with the inverse variance weighted (IVW) method, and MR-Egger, weighted median (WM), and MR-PRESSO were performed as sensitivity analyses.

Results

The Phylum Verrucomicrobia (OR 1.27, 95%CI 1.01 to 1.61; p = 0.04), Genus Defluviitaleaceae UCG011 (OR 1.29, 95%CI 1.04 to 1.59; p = 0.02), and Genus Coprococcus 3 (OR 1.44, 95%CI 1.02 to 2.05; p = 0.04) was a risk effect against urticaria. And Order Burkholderiales (OR 0.68, 95%CI 0.49 to 0.99; p = 0.04) and Genus Eubacterium xylanophilum group (OR 0.78, 95%CI 0.62 to 0.99; p = 0.04) were negatively associated with urticaria, suggesting a protective effect. At the same time, urticaria had a positively causal effect on gut microbiota (Genus Eubacterium coprostanoligenes group) (OR 1.08, 95%CI 1.01 to 1.16; p = 0.02). These findings showed no influence by heterogeneity or horizontal pleiotropy. Moreover, most sensitivity analyses showed results consistent with those of IVW analysis.

Conclusion

Our MR study confirmed the potential causal relationship between gut microbiota and urticaria, and the causal effect was bidirectional. Nevertheless, these findings warrant further examination owing to the unclear mechanisms.

Association of Gut Lachnospiraceae and Chronic Spontaneous Urticaria

(1) Background: Chronic spontaneous urticaria (CSU) has been linked to the dysbiosis of the gut microbiota. Furthermore, various studies have highlighted the anti-inflammatory properties of short-chain fatty acids (SCFAs), whose production is primarily regulated by the gut microbiota. However, only a few studies have investigated the role of major SCFA producers, such as Lachnospiraceae, in skin inflammatory diseases. (2) Goal: This study aimed to compare the abundance of Lachnospiraceae between CSU patients and healthy controls (HCs). (3) Material and methods: In this case-control study, 16S rRNA sequencing was performed to compare the composition of the gut microbiome between 22 CSU patients and 23 HCs. (4) Results: Beta-diversity revealed significant clustering (p < 0.05) between the CSU patients and HCs. Alpha diversity in the CSU group was significantly decreased according to the Evenness index (p < 0.05). The linear discriminant analysis effect size (LEfSe) identified the significant depletion of the Lachnospiraceae family in CSU patients. (5) Conclusion: Our study revealed the dysbiosis of the gut microbiota in CSU patients, including decreased levels of Lachnospiraceae members, responsible for SCFA production, suggesting that SCFAs may contribute to immune dysfunction in the pathogenesis of CSU. We speculate that the modulation of SCFAs could serve as a prospective additional option in CSU treatment.

Association of Gut Lachnospiraceae and Chronic Spontaneous Urticaria

(1) Background: Chronic spontaneous urticaria (CSU) has been linked to the dysbiosis of the gut microbiota. Furthermore, various studies have highlighted the anti-inflammatory properties of short-chain fatty acids (SCFAs), whose production is primarily regulated by the gut microbiota. However, only a few studies have investigated the role of major SCFA producers, such as Lachnospiraceae, in skin inflammatory diseases. (2) Goal: This study aimed to compare the abundance of Lachnospiraceae between CSU patients and healthy controls (HCs). (3) Material and methods: In this case–control study, 16S rRNA sequencing was performed to compare the composition of the gut microbiome between 22 CSU patients and 23 HCs. (4) Results: Beta-diversity revealed significant clustering (p < 0.05) between the CSU patients and HCs. Alpha diversity in the CSU group was significantly decreased according to the Evenness index (p < 0.05). The linear discriminant analysis effect size (LEfSe) identified the significant depletion of the Lachnospiraceae family in CSU patients. (5) Conclusion: Our study revealed the dysbiosis of the gut microbiota in CSU patients, including decreased levels of Lachnospiraceae members, responsible for SCFA production, suggesting that SCFAs may contribute to immune dysfunction in the pathogenesis of CSU. We speculate that the modulation of SCFAs could serve as a prospective additional option in CSU treatment.

Chimonanthus nitens Oliv Polysaccharides Modulate Immunity and Gut Microbiota in Immunocompromised Mice

To investigate the immunomodulatory activities of Chimonanthus nitens Oliv polysaccharides (COP1), an immunosuppressive mouse model was generated by cyclophosphamide (CY) administration and then treated with COP1. The results demonstrated that COP1 ameliorated the body weight and immune organ (spleen and thymus) index of mice and improved the pathological changes of the spleen and ileum induced by CY. COP1 strongly stimulated the production of inflammatory cytokines (IL-10, IL-12, IL-17, IL-1β, and TNF-α) of the spleen and ileum by promoting the mRNA expressions. Furthermore, COP1 had immunomodulatory activity by increasing several transcription factors (JNK, ERK, and P38) in the mitogen-activated protein kinase (MAPK) signaling pathway. Related to the above immune stimulatory effects, COP1 positively affected the production of short-chain fatty acids (SCFAs) and the expression of ileum tight junction (TJ) protein (ZO-1, Occludin-1, and Claudin-1), upregulated the level of secretory immunoglobulin A (SIgA) in the ileum and microbiota diversity and composition, and improved intestinal barrier function. This study suggests that COP1 may provide an alternative strategy for alleviating chemotherapy-induced immunosuppression.

Changes of Gut Microbiome in Adolescent Patients with Chronic Spontaneous Urticaria After Omalizumab Treatment

Purpose

Omalizumab is a humanized anti-immunoglobulin (Ig) E monoclonal antibody that is effective in treating some patients with chronic spontaneous urticaria (CSU) who do not respond to antihistamines. Gut microbiome plays a role in the pathogenesis of allergies and autoimmune diseases. Here, we investigated differences in the gut microbiome of adolescent CSU patients before and after omalizumab treatment, which has not been previously reported.

Patients and Methods

Ten adolescent CSU patients were given 300 mg omalizumab subcutaneously in three treatments at 4-week intervals. Urticaria Activity Score (UAS7) was applied to evaluate the efficacy of each omalizumab treatment during follow-up. Fecal samples were collected before and 12 weeks after the first treatment. Total DNA of the gut microbiota in all fecal samples were extracted. The 16S rRNA gene-targeted sequencing technology was used for the analysis of the diversity and distribution of gut microbiome, followed by bioinformatics analysis.

Results

UAS7 scores decreased significantly after each treatment compared with the baseline (all P < 0.0001). There were five well-controlled responders and five non-responders after three treatment sessions of omalizumab. The dominant bacteria phyla in all fecal samples were Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Alpha diversity analysis showed no significant difference before and after treatment (P > 0.05), whereas beta diversity analysis revealed a significant difference in the bacterial abundance before and after treatment (P < 0.01). The relative abundance of Alphaproteobacteria and Betaproteobacteria at the class level and Burkholderia, Rhodococcus, and Sphingomonas at the genus level decreased significantly after treatment (linear discriminant analysis > 4, P < 0.05). The functional prediction results showed that the dioxin and xylene degradation pathways were more abundant before treatment.

Conclusion

Omalizumab is effective in treating CSU and the abundance of Alphaproteobacteria and Betaproteobacteria was reduced after treatment, which may help improve the treatment outcomes in adolescent CSU patients.

The role of short-chain fatty acids in inflammatory skin diseases

Short-chain fatty acids (SCFAs) are metabolites of gut microbes that can modulate the host inflammatory response, and contribute to health and homeostasis. Since the introduction of the gut-skin axis concept, the link between SCFAs and inflammatory skin diseases has attracted considerable attention. In this review, we have summarized the literature on the role of SCFAs in skin inflammation, and the correlation between SCFAs and inflammatory skin diseases, especially atopic dermatitis, urticaria, and psoriasis. Studies show that SCFAs are signaling factors in the gut-skin axis and can alleviate skin inflammation. The information presented in this review provides new insights into the molecular mechanisms driving gut-skin axis regulation, along with possible pathways that can be targeted for the treatment and prevention of inflammatory skin diseases.

Combined microbiome and metabolome analysis of gut microbiota and metabolite interactions in chronic spontaneous urticaria

Background

The pathogenesis of chronic spontaneous urticaria (CSU) is unclear, and it turned out to be involved in biological processes, such as autoimmunity, autoallergy, inflammation, and coagulation. The gut microbiota plays an important role in immune and inflammatory diseases. However, the relationship between chronic spontaneous urticaria and the gut microbiota remains unknown.

Methods

The stool and serum samples were taken from 15 CSU patients and 15 normal controls. Changes in the composition of gut microbiota and serum metabolism in CSU patients and normal controls were analyzed by 16S ribosomal RNA (rRNA) gene sequencing and untargeted metabolomics.

Results

The results of 16S rRNA gene sequencing showed that compared with normal controls, CSU patients had increased α-diversity of gut microbiota and significant differences in β-diversity. At the phylum level, the relative abundance of Firmicutes increased and the relative abundance of Bacteroidetes and Proteobacteria decreased in CSU patients compared with healthy controls. At the genus level, six kinds of bacteria were significantly enriched in CSU patients and five in normal controls. Metabolomic analysis revealed altered levels of metabolites such as unsaturated fatty acids and purines. Correlation analysis of gut microbiota and metabolites showed that Lachnospira was negatively correlated with arachidonic acid, and Gemmiger was also negatively correlated with (±)8-HETE.

Conclusion

This study suggests that changes in gut microbiota and metabolites may play a role in immune and inflammatory pathways in the pathogenesis of CSU patients.

Gut Microbiome Composition in Patients with Chronic Urticaria: A Review of Current Evidence and Data

Recent studies have linked gut microorganism composition and chronic urticaria (CU); 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 (a dysbiosis) could influence the course of chronic spontaneous urticaria (CSU), 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 CSU, though only a few have exhibited metabolic abnormalities associated with gut dysbiosis. The studies on CSU 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). In addition, serum metabolome analysis revealed that gut microbiota-associated alterations in unsaturated fatty acids and the butanoate metabolism pathway may play a role in CSU. These findings are potentially associated with inflammation mediated by the imbalance of Th1/Th2/Th17 cytokines, which might contribute to CSU pathogenesis. Further research in this field could improve clinical, diagnostic, and therapeutic approaches to patients with CSU. By applying new knowledge on gut microbial communities and metabolomics, future CSU therapies could modify the microbiota composition using agents such as probiotics or other similar agents, which, in combination with current standard therapies, could hopefully lead to a reduction in symptoms and an improved quality of life for CSU patients.

Seasonal differences in intestinal flora are related to rats' intestinal water metabolism

Many studies have reported obvious seasonal differences in the intestinal flora of rats, and this stable distribution of the seasonal flora helps in maintaining the normal physiological function of the host. However, the mechanism underlying these seasonal differences in intestinal flora remains unclear. To explore the correlation among seasonal factors and intestinal water metabolism and intestinal flora, 20 Sprague Dawley (SD) rats were divided into spring, summer, autumn, and winter groups. The environment for the four seasons was simulated using the Balanced Temperature and Humidity Control system. The intestinal water metabolism was evaluated by determining the intestinal transmission function, fecal water content, water content of colonic tissue, and the colonic expression levels of AQP3, AQP4, and AQP8. The composition and relative abundance of intestinal microflora in rats in each season were assessed through 16S rDNA amplifier sequencing, and the relationship between the dominant flora and intestinal water metabolism in each season was analyzed using Spearman correlation analysis. The high temperature and humidity season could lead to an increase in intestinal water metabolism and intestinal water content in rats, whereas the low temperature and humidity season could lead to a decrease, which was closely related to the change in microflora. To explore the molecular mechanism of seasonal changes in intestinal water metabolism, the concentration of colonic 5-HT, VIP, cAMP, and PKA associated with intestinal water metabolism in rats were also examined. Seasonal changes could affect the concentration of colonic 5-HT and VIP in rats, and then regulate AQPs through cAMP/PKA pathway to affect the intestinal water metabolism. These results suggest that seasonal factors affect the level of intestinal water metabolism in rats and result in seasonal differences in intestinal flora.

Alterations of gut microbes and their correlation with clinical features in middle and end-stages chronic kidney disease

Gut microecosystem has been shown to play an important role in human health. In recent years, the concept of the gut-kidney axis has been proposed to explain the potential association between gut microbiota and chronic kidney disease (CKD). Here, a cohort of fecal samples collected from patients with CKD (n = 13) were involved. The composition of gut microbial communities and clinical features in CKD and end-stage renal disease (ESRD) were characterized. Our study focused on the changes in gut microbiome and the correlation with clinical features in patients with CKD and ESRD by analyzing high-throughput sequencing results of collected feces. We elucidated the alterations of gut microbiota in CKD patients at different stages of disease and initially identified the gut microbiota associated with CKD progression. We also combined correlation analysis to identify clinical features closely related to the gut microbiome. Our results offered the possibility of using non-invasive gut microbiome in the early diagnosis of course from CKD to ESRD and provide new insights into the association between clinical features and gut microbiota in CKD.

Altered Gut Microbiota in H1-Antihistamine-Resistant Chronic Spontaneous Urticaria Associates With Systemic Inflammation

Background and Objective

Chronic spontaneous urticaria (CSU) is a histamine-mediated inflammatory skin disease, and second-generation non-sedating H1-antihistamines (nsAH) at licensed doses have long been the first-line therapy in CSU. However, about 50% of patients are resistant to nsAH, and the precise pathogenesis remains largely unknown but seems to be associated with low-level systemic or intestinal inflammation. We aim to determine the fecal microbial composition and clarify its correlation with the clinical profiles og CSU with nsAH resistance.

Methods

A total of 25 CSU patients with or 19 CSU patients without nsAH resistance and 19 healthy controls (HC) were enrolled in this study. The intestinal microbiome was detected by 16S rRNA sequencing. The data were analyzed using R language software.

Results

Significantly higher urticarial activity score for 7 days, stool calprotectin, erythrocyte sedimentation rate, serum C-reactive protein, and interleukin-6, but much lower alpha-diversity and evenness of fecal bacterial community were observed in CSU patients with nsAH resistance than in those without (P <0.05 for all variables). Compared to patients with nsAH-responsiveness, the abundance of fecal genera Prevotella, Megamonas, and Escherichia were significantly increased, while that of Blautia, Alistipes, Anaerostipes, and Lachnospira were remarkably reduced in nsAH-resistant patients (uncorrected P <0.05 for all variables). Finally, systemic not intestinal inflammation degree was positively correlated with genera Escherichia, while negatively with genera Blautia, Dorea, Lactobacillus, Eubacterium_hallii_group, and Roseburia. CSU without nsAH resistance and HC individuals showed almost unchanged genera bacterium.

Conclusions

Among CSU patients, pro-inflammation phenotype relating to enteric dysbacteriosis features nsAH resistance in CSU patients. The results provide clues for future microbial-based or anti-inflammatory therapies on nsAH resistant CSU.

Investigation of intestinal microbiome in chronic spontaneous urticaria patients

BACKGROUND

Chronic urticaria is a disorder characterized by itchy erythematous plaques with edema lasting 6 weeks or more. The prevalence is 1%, and two thirds of these cases are "chronic spontaneous urticaria (CSU)." Drugs, food, infections, and systemic diseases may be etiologic factors for CSU, although it may be idiopathic.

OBJECTIVES

The aim of this study was to compare the diversity and distribution of the intestinal microbiome in CSU patients with that of healthy individuals. The hypothesis was to determine the probable association of intestinal microbiome with CSU.

METHODS

This study was conducted in Sakarya University Training and Research Hospital, Department of Dermatology. In this study, 20 CSU patients and 10 healthy volunteers were included. Stool samples were collected from all participants. 16S RNA sequencing and bioinformatic analysis were performed after isolation of DNA isolation from all samples.

RESULTS

Diversity in microorganisms, stool pH averages, Bristol scores, and the ratio of Firmicutes/Bacteroidetes were the significant changes between the two groups.

LIMITATIONS

Due to high cost involved in microbiota studies, only a limited number of patients and volunteers participated.

CONCLUSION

The alteration in the intestinal microbiota (dysbiosis) may be an essential factor for CSU development and may explain idiopathic cases.

Salivary Microbiota Is Significantly Less Diverse in Patients with Chronic Spontaneous Urticaria Compared to Healthy Controls: Preliminary Results

Background: Because of the important role in regulating the immune system, increasing evidence suggests a possible implication of gut microbiota in Chronic spontaneous urticaria (CSU). Although the oral cavity is the first site of contact between microbiota and the immune system, the association between salivary microbiota and CSU has not yet been reported. Objective: This case-control study aimed to compare differences in salivary microbiota between CSU patients and healthy controls (HC). Twenty-three participants—13 patients with CSU and 10 HC were enrolled; salivary microbiota was determined by molecular approach targeting 16S ribosomal RNA. Terminal restriction fragment length polymorphism (T-RFLP) analysis was performed. Results: Alpha diversity of salivary microbiota in CSU patients was significantly reduced compared to HC, resulting in alteration of the community composition. Species richness determined via the Shannon index was significantly reduced in the CSU group. Conclusion: Dysbiosis of salivary microbiota may contribute to a dysregulated immune system in the development of CSU. To our knowledge, this was the first study that reported an alteration in salivary microbiota composition in CSU patients.