Modulating the lung–gut axis: A randomized controlled trial of Xie Bai Zeng Ye decoction on intestinal flora and mucosal immunity in children with post-infectious cough

BACKGROUND: This study aimed to evaluate the clinical efficacy of Xie Bai Zeng Ye Decoction (XBZY) in the treatment of post-infectious cough in children with lung heat and Yin deficiency, and to investigate its effects on gut microbiota composition and intestinal mucosal barrier function. METHODS: A total of 116 children diagnosed with post-infectious cough due to lung heat and Yin deficiency were enrolled and randomly assigned to either a XBZY group or a Montelukast Sodium control group. Both groups received treatment for 10 consecutive days. Clinical outcomes were assessed using the Cough Evaluation Test, Visual Analogue Scale, Traditional Chinese Medicine (TCM) syndrome scores, and the Chinese version of the Leicester Cough Questionnaire, both before and after treatment. In addition, serum D-lactic acid levels were measured as an indicator of intestinal permeability. Fecal samples were collected to quantify the abundance of Lactobacillus, Bifidobacterium, and Escherichia coli, and to determine the levels of short-chain fatty acids, including acetate, propionate, and butyrate. RESULTS: Both groups demonstrated significant improvements in clinical symptoms after treatment. Compared to the Montelukast Sodium group, children in XYZB group exhibited significantly lower Visual Analogue Scale and TCM syndrome scores, as well as higher Leicester Cough Questionnaire scores. The mean cough disappearance time was shorter, and the cough disappearance rate was significantly higher in XBZY group. Furthermore, serum D-lactic acid levels decreased significantly after treatment in XBZY group, while levels of Lactobacillus and Bifidobacterium increased and Escherichia coli decreased. Short-chain fatty acid concentrations, including acetate, propionate, and butyrate, were also significantly elevated in the XYZB group compared to controls. CONCLUSION: This exploratory study suggests that XBZY may be a promising treatment option for children with post-infectious cough characterized by lung heat and Yin deficiency. Compared with Montelukast Sodium, XBZY demonstrated superior short-term improvements in cough resolution, symptom relief, quality of life, intestinal barrier function, and gut microbiota modulation, while maintaining good safety. These findings highlight the potential role of the lung-gut axis in pediatric respiratory care and support the integration of TCM-based strategies; however, larger, blinded, and longer-term studies are needed to validate these results and assess their broader clinical applicability.