Environmental factors influencing the microbiome in adult asthma: emerging mechanistic insights

Purpose of review Asthma is a mosaic of phenotypes shaped by complex host–environment interactions. Among these, the microbiome has moved to a central determinant of disease expression, and airway and gut microbiome should be seen as active players in asthma pathophysiology. This review critically examines how environmental exposures, including pollution, drugs, diet, and climate, remodel microbial ecosystems, and reprogram immune responses in adults with asthma, with emphasis on clinical translation. Recent findings Advances from multiomics, large-scale cohorts, and Mendelian randomization studies reinforce the concept of the gut-lung axis as a decisive modulator of asthma outcomes. Airway dysbiosis, often marked by Proteobacteria dominance, consistently correlates with poor asthma control, exacerbations, and steroid resistance. Environmental determinants of microbiome reshape erode immune tolerance. Microbial metabolites such as short-chain fatty acids act as molecular messengers capable of restoring epithelial and immune balance. These findings challenge the traditional inflammatory-centric view of asthma and demand broader mechanistic frameworks. Summary The microbiome should be considered a central piece of the puzzle in asthma research. Precision medicine in adult asthma will remain aspirational unless microbiome-informed biomarkers and interventions are embraced. Robust interventional studies are urgently needed to translate this promise into practice.