Pollen-i nduced allergic rhinitis affects around 25–30% of the European population, whilst estimates of fungal sensitization is around 10–15%. Depending on the geographical region, pollen and fungal spore seasons may differ in their timing, however in some areas they may partially overlap causing an increased risk of a multi-allergen exposure for allergic individuals. The main aim of our study was to determine the spatial patterns of season timing and the frequency of co-occurrence of airborne pollen and fungal spores in Europe.