Start, duration, and intensity of different pollen seasons (PSs) can significantly differ between countries and regions with a high grade of annual variety over the longitudinal course.1 This is mainly influenced by factors such as climate, vegetation, urbanization, pollution, and others. The documentation of long-term chanStart, duration, and intensity of different pollen seasons (PSs) can significantly differ between countries and regions with a high grade of annual variety over the longitudinal course.1 This is mainly influenced by factors such as climate, vegetation, urbanization, pollution, and others. The documentation of long-term changes in pollen flight is influenced by the method used to define a PS.

Airborne pollen is measured commonly using Hirst-type volumetric spore traps2 according to national3 and European Union standards.4 The results are usually expressed as average daily pollen concentrations of different pollen taxa (in pollen grains/m3 of air), which can be used to calculate the start and end of the PS. However, the above-mentioned variability of confounding factors is an obstacle to an overarching, generally accepted definition.1 Several PS definitions, serving difference scientific purposes, are in use,5 but have not been validated with respect to allergen immunotherapy (AIT).6ges in pollen flight is influenced by the method used to define a PS.

Airborne pollen is measured commonly using Hirst-type volumetric spore traps2 according to national3 and European Union standards.4 The results are usually expressed as average daily pollen concentrations of different pollen taxa (in pollen grains/m3 of air), which can be used to calculate the start and end of the PS. However, the above-mentioned variability of confounding factors is an obstacle to an overarching, generally accepted definition.1 Several PS definitions, serving difference scientific purposes, are in use,5 but have not been validated with respect to allergen immunotherapy (AIT).6