Axillary and gut microbiota characteristics in axillary bromhidrosis patients and the effect of microwave therapy: a case-control study

IntroductionAxillary bromhidrosis is characterized by excessive sweat gland activity and foul body odor, significantly affecting patients’ psychological well-being and social interactions.MethodsThis study recruited 30 axillary bromhidrosis patients and 30 healthy controls, collecting sweat and stool samples for microbiome analysis. Among the patients, 8 patients received microwave therapy, collecting pre- and post-treatment samples for microbiome analysis.ResultsThe axillary microbiota of patients showed significant differences compared to healthy controls, particularly with increased abundance of odor-causing bacteria such as Staphylococcus and related species (Staphylococcus hominis, Staphylococcus haemolyticus) (LDA > 3, p < 0.05). While the gut microbiota composition showed no significant changes, but LEfSe analysis revealed that SCFAs-producing bacteria (Bacteroides stercoris, Phocaeicola massiliensis, and Phocaeicola vulgatus) was significantly elevated (LDA > 3, p < 0.05), indicating that the abundance changes of SCFAs-producing bacteria may be associated with axillary odor production through the regulation of metabolic processes. Correlation analysis revealed positive correlations between axillary odor-producing genera (Staphylococcus, Peptoniphilus, Anaerococcus) and gut SCFAs-producing genera (Roseburia, Blautia, Clostridium), suggesting a bidirectional microbiota network through gut-derived butyrate production and immune modulation (p < 0.05). However, further experimentals are required to confirm the causal relationship. Furthermore, microwave therapy significantly altered axillary microbiota diversity, potentially alleviating axillary odor by inhibiting odor-producing bacteria (Staphylococcus) (LDA > 3, p < 0.05), while exerting minimal impact on the gut microbiota. KEGG pathway enrichment analysis revealed significant metabolic activity changes in lipid, carbohydrate, sulfur, and amino acid metabolism pathways.ConclusionThis study is the first to demonstrate the interrelationship between the axillary and gut microbiota in axillary bromhidrosis patients, showing a link between gut-derived butyrate production and axillary odor. These findings offer new insights into the microbiological mechanisms underlying axillary bromhidrosis and identify potential microbial targets for future gut-based systemic treatments.