A significant number of individuals, approximately 7 million in South Korea, suffer from allergic rhinitis, a condition that has seen an 18-fold increase over the past two decades, affecting one in five citizens. Traditionally thought to be caused primarily by allergic reactions, emerging science attributes the root cause of allergic rhinitis to the disruption of the microbial ecosystem within the nasal cavity. The nasal mucosa hosts around 900 species and 30,000 microorganisms, with beneficial bacteria like Corynebacterium playing a crucial role in immune defense by secreting antimicrobial substances to fend off pathogens.

New studies are introducing the 'Nasal-Gut Microbiome Axis' concept, adding to previously acknowledged gut-brain and gut-vagina-bladder axes, suggesting a complex interconnection between gut health and nasal microbiome stability. A review to be published in 2025 will highlight how short-chain fatty acids produced by beneficial gut bacteria can influence nasal immune responses via the bloodstream, demonstrating a bi-directional relationship where imbalances in the nasal microbiome can also affect gut immunity. This reflects findings from a systematic review indicating significant differences in microbial diversity between rhinitis patients and healthy individuals, pointing to a state of dysbiosis where harmful bacteria like Staphylococcus aureus proliferate at the expense of protective species.

Regular habits such as using antimicrobial mouthwash may disrupt the natural microbial balance in the oral and nasal cavities, as warned in a Cochrane systematic review, raising concerns about their long-term health implications. The research emphasizes a more beneficial strategy that focuses on supplementing healthy bacteria rather than applying antimicrobial agents that could further disrupt the ecosystem, thereby indicating a potential shift in treatment strategies for allergic rhinitis towards maintaining or restoring microbial diversity.