Our study showed that indoor sensitization is higher than outdoor sensitization in the Central Anatolia region, with house dust mite (Df) sensitization being the most common indoor aeroallergen, and grass mix sensitization being the most common outdoor aeroallergen. When we examined the distribution over the years, we observed that cat allergy has increased over the years, especially in the post-COVID-19 period.
Climate, geography, and vegetation influence atmospheric aeroallergen content 3. An evaluation of 2,554 plant samples collected on Mount Erciyes between 1996 and 2002 identified 1170 species and subspecies taxa (1116 species, 31 subspecies, 23 variants) belonging to 89 families and 433 genera. The largest families in terms of the number of species and subspecies taxa are Asteraceae, Fabaceae, and Poaceae 10.
Poaceae pollen (grass pollen) is currently among the leading aeroallergens worldwide and is the primary cause of pollen allergy in most developed countries, particularly in North America and Europe 11. Consistent with global data, we observed the highest rate of sensitization to grass pollen among outdoor aeroallergens.
Olea europaea pollen is a significant cause of respiratory allergic diseases in the Mediterranean region; olive pollen is a significant cause of pollinosis in Spain, Southern Italy, Greece, and Türkiye 12. Although Kayseri is not located in a coastal area, olive tree sensitization is significantly common 9. Our patients experienced sensitization in 32.8% of those tested with olive aeroallergen.
Previous studies have shown an increase in the prevalence of both cat ownership and cat allergy during the COVID-19 period 13,14. Our study did not compare pre-COVID-19 with those during or after COVID-19, but consistent with the literature, we observed that the upward trend in cat sensitization continued even after the COVID-19 pandemic lockdowns ended.
Moreover, the frequency of outdoor aeroallergens was found to be higher in the pre-COVID-19 period, likely due to the impact of curfews, and this was similar to other studies conducted during the COVID-19 period (15, 16). The frequency of Dp aeroallergens was found to be significantly lower in 2024 and 2021 compared to 2022.
When evaluated monthly, the frequency of indoor aeroallergens in June was significantly lower than in January, February, March, August, October, November, and December, and the frequency in May was lower than in January, February, March, and December. Several studies of allergic patients have reported higher rates of IgE sensitization to pollen or higher specific IgE (sIgE) levels during or after the pollen season 17. At the regional level, evidence suggests that sIgE for both grass and birch pollen varies seasonally (higher levels in spring and potentially higher levels in summer than winter) 18. Similarly, in our study, grass pollen aeroallergen sensitization peaked in June and birch aeroallergen sensitization peaked in July.
The overall outdoor environment encompasses factors such as climate, biodiversity, and urban, social, and economic conditions that shape human interactions with the natural world 19. One notable health impact is the increase in allergic respiratory diseases triggered by increased atmospheric carbon dioxide and higher temperatures. These factors increase the concentration and aeroallergenicity of airborne particles such as pollen and fungal spores, leading to more severe symptoms 20. Higher temperatures before the pollen season have been associated with earlier pollen release 21. Furthermore, rain, wind, and sun may have contributed to the extension of the pollen season 22. There are studies indicating that grass and birch pollen seasons may be altered due to climate change, starting earlier and producing greater amounts 23,24. However, despite these findings, we have not found any evidence demonstrating the effect of changes in pollen release timing on the sensitization profile. Studies spanning many years are likely necessary to observe this effect.
In patients with pollen monosensitization, symptoms persist only in the spring, while in patients with polysensitization, symptoms persist for several months or years 25. There are studies suggesting that monosensitization and polysensitization constitute two distinct phenotypes of AR, and polysensitization has been significantly associated with moderate to severe persistent AR 26. According to our data, the proportion of polysensitized patients was higher than that of monosensitized patients among those sensitized to both indoor and outdoor aeroallergens. However, because our clinic is located in a tertiary hospital, we believe that the higher proportion of polysensitized patients is likely due to the higher referral rate of patients with moderate and severe persistent rhinitis.
Although previous studies have shown no association between induration diameter and clinical symptoms 27,28, we observed grass pollen diameter was significantly higher than other pollen aeroallergens.
Our study is valuable because it covers a total of 4 years, including a high patient participation rate, and especially data from the COVID-19 period, when people spent more time indoors. Aeroallergen sensitization was evaluated not only in patients residing in Kayseri province but also in other cities in Central Anatolia. Due to the retrospective nature of the study, detailed clinical findings and comorbidities of the patients could not be evaluated. Furthermore, due to seasonal variations in the brands and types of aeroallergen solutions provided by the institution, not all aeroallergens could be applied to all patients.
The diversity of our findings suggests that aeroallergen protection measures can be developed based on regional sensitization differences. In the coming years, there is a need for studies with wider participation, which will map detailed aeroallergen sensitization, especially pollen, according to the geographical characteristics of Türkiye.
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