Background: Grasses (Poaceae) are one of the largest plant families and are distributed worldwide. Grass pollen allergy is one of the most important pollen allergies affecting large parts of the population worldwide. The grass pollen season itself is special since it is caused by the flowering of various grass species that present unique profiles of allergenicity, which assumingly plays a significant role and impact on grass pollen sensitization profiles for the allergy sufferer. The aim of this study, conducted in Vienna, 2014, was to analyze the possible contribution of prevalent grass species to the grass pollen season and to the symptom load of grass allergy sufferers. Methods: This was the first study that combines phenological observations (i.e. grass species and their flowering periods) with aerobiological measurements (i.e. daily grass pollen concentrations) in concert with allergic symptoms from local users of the Patient's Hayfever Diary (symptom load index calculation). Results: Both the pollen concentrations and the symptom levels were higher in the first half of the main grass pollen season and therefore show the highest impact on pollen allergy sufferers. Of important note were the following species that are widely distributed in Vienna: Kentucky bluegrass (Poa pratensis), orchard grass (Dactylis glomerata), false oat-grass (Arrhenatherum elatius), fescue grass (Festuca sp.) and perennial rye-grass (Lolium perenne). Conclusion: Monitoring different grass species provided evidence for varying contribution in pollination across the main grass pollen season and highlighted the significance this impact may have on pollen allergy sufferers. (C) 2016 Elsevier B.V. All rights reserved.