Gut microbiota dysbiosis and the gut–lung axis: links to asthma and its common comorbidities

Asthma is a heterogeneous chronic inflammatory airway disease that frequently coexists with multiple comorbidities, including obesity, allergic rhinitis, chronic rhinosinusitis, and gastroesophageal reflux disease (GERD). These conditions substantially increase disease burden and complicate asthma management. Increasing evidence suggests that gut microbiota dysbiosis represents a shared biological factor linking asthma and its comorbidities through immune and metabolic pathways operating along the gut–lung axis. This narrative review summarizes current knowledge on how alterations in gut microbial composition and function influence immune homeostasis, chronic inflammation, and disease susceptibility in asthma and its common comorbid conditions. Particular emphasis is placed on microbial metabolites such as short-chain fatty acids, early-life immune programming, bidirectional gut–lung immune communication, and emerging microbiota-targeted interventions. Understanding the systemic role of the gut microbiota may provide novel insights into integrated prevention and management strategies for asthma and its comorbidities.