Floral biology variations in Olea europaea over 6 years in Southern Italy: implications for allergy

Aim: Olea europaea, an endemic plant of the Mediterranean basin, exhibits a flowering period from April to June, requiring high temperatures and sensitivity to low humidity, rainfall, and windiness. Allergy to O. europaea affects 13.85% of the Southern Italian population. This study investigated O. europaea pollen concentration, morphological and biochemical variations, and clinical symptoms over a 6-year period (2017–2022). Methods: Pollen concentration in Southern Italy (Apulia, Bari) was analyzed alongside weather variables (temperature, precipitation, humidity, and windiness) using existing databases (Arpa Puglia; time and date). Optical and fluorescence microscopy techniques were employed to assess pollen morphology and biochemical characteristics. Additionally, the absolute number of prescriptions for various antihistamine drugs (cetirizine, ebastine, bilastine, desloratadine, rupatadine, levocetirizine, fexofenadine, loratadine) was calculated. Results: The lowest pollen count occurred in the 2018 (91.1 pollen per m3/week), while the highest was recorded in the 2021 (2,545.3 pollen per m3/week). In 2019, the pollen peak was delayed by 2 weeks. Notably, 2018 exhibited more rainy days in May and June and higher humidity percentages (April 73%, May 70%, June 72%). In contrast, 2021 had lower humidity values (April 68%, May 61%, June 59%) and fewer rainy days (1 day in May and none in June). No changes in pollen size were observed, but modifications in O. europaea pollen fuchsin fluorescence were noted in 2018 and 2021. The number of drug prescriptions was highest in 2021. Conclusions: This study highlights that the flowering period, morphology, and pollen production of O. europaea may influence patient symptomatology and the need for antihistamine medications.