Hold my paw: the unseen exchange in our homes and its impact on health

The human-animal bond represents a topic of growing scientific and public health relevance, as companion animals share close living environments with humans in a substantial proportion of households across many countries. This intimate cohabitation creates a shared microbial environment, facilitating constant, bidirectional exchange of microorganisms between pets and their owners. Here, we explore the dynamics of this microbial transfer and its influence on human health, specifically focusing on  immune-mediated, metabolic, and gastrointestinal disorders. Drawing from the  “One Health” concept, which recognizes the interconnectedness of human, animal, and environmental health, we examine how companion animals shape the composition of the human gut microbiota. Evidence suggests that while this exchange carries potential risk for transmitting pathogens and antimicrobial resistance, the overall effect appears beneficial. Pet exposure, particularly in early life, is associated with increased microbial diversity and enrichment of beneficial taxa such as Ruminococcus and Oscillospira. These alterations are linked to reduced risk of immune-mediated conditions like allergies and asthma, consistent with the ”microbiota hypothesis”. Furthermore, pet ownership correlates with lower prevalence of metabolic syndrome, potentially mediated by favorable shifts in gut microbiota, such as a reduced Firmicutes-to-Bacteroidetes ratio. However, household transmission of extended-spectrum β-lactamase-producing Enterobacterales represents a tangible public health concern requiring antimicrobial stewardship. We synthesize current findings, highlighting the household as a key epidemiological unit and positioning the shared microbiome as a critical factor in health outcomes of pet-owning families.