The Microbiome of the Nose—Friend or Foe?

Recently, multiple studies regarding the human microbiota and its role on the development of disease have emerged. Current research suggests that the nasal cavity is a major reservoir for opportunistic pathogens, which can then spread to other sections of the respiratory tract and be involved in the development of conditions such as allergic rhinitis, chronic rhinosinusitis, asthma, pneumonia, and otitis media. However, our knowledge of how nasal microbiota changes originate nasopharyngeal and respiratory conditions is still incipient. Herein, we describe how the nasal microbiome in healthy individuals varies with age and explore the effect of nasal microbiota changes in a range of infectious and immunological conditions. We also describe the potential health benefits of human microbiota modulation through probiotic use, both in disease prevention and as adjuvant therapy. Current research suggests that patients with different chronic rhinosinusitis phenotypes possess distinct nasal microbiota profiles, which influence immune response and may be used in the future as biomarkers of disease progression. Probiotic intervention may also have a promising role in the prevention and adjunctive treatment of acute respiratory tract infections and allergic rhinitis, respectively. However, further studies are needed to define the role of probiotics in the chronic rhinosinusitis.