Pollen and Fungal Spore Co-Exposure in Allergic Respiratory Diseases: A Systematic Review

Co-exposure to airborne pollen and fungal spores is increasingly recognized as a contributor to asthma and allergic rhinitis, especially as climatic shifts since 2020 have intensified their seasonal overlap. We systematically searched PubMed and Google Scholar for studies published between 2020 and 2025 that assessed simultaneous pollen–fungi exposure and respiratory outcomes. Screening was performed independently by two reviewers, resulting in 12 eligible studies out of 320 records. Meta-analysis was not feasible due to substantial heterogeneity in exposure definitions, taxa, outcome measures, and analytical approaches. Overall, the studies indicate that short-term co-exposure tends to worsen respiratory symptoms and increase emergency visits or asthma exacerbations, with stronger effects in children, polysensitized individuals, and urban settings. However, effect sizes varied considerably across regions and methodologies. Environmental and climatological papers provided context for seasonal overlap but did not contribute clinical data. Current evidence suggests a potential synergistic effect, though more standardized exposure metrics are needed to refine risk estimates.