AbstractHuman microbiome contributes to critical functions that impact health and disease. It influences the development of the immune system, and the pathogenesis of immunological disorders included allergy. While it is easy to understand how airway microbiome, influencing local inflammation and immune activity, could contribute to shaping asthma phenotype, it is not so obvious to understand the influence by the gut microbiome, but there is growing evidence about it. The increase of allergic disorders in western countries led to investigate the role environment is playing and how it may change our microbiome and immune system, with the hope of finding new preventive approaches for allergy.