Monitoring disease activity of pollen allergies: What crowdsourced data are telling us.

Background: Pollen allergies are a major public health concern worldwide. An IgE-mediated systemic inflammatory response to pollen allergens causes symptoms of allergic rhinitis or even asthma. They have a significant impact on individual quality of life and cause high socioeconomic strain. The aim of this study was to examine the value of pollen allergy-related web search data for public health. Methods: An in-depth analysis of search volumes and contents, and their correlation with factors of disease activity such as rates of dispensed medicine and pollen concentration, was conducted. In this retrospective longitudinal study, Google Ads Keyword Planner was used to determine the internet search volume of terms related to pollen allergies across Germany and Sweden as a whole and in each of the 16 German federal states and 21 Swedish provinces between January 2017 and December 2020. This search volume was converted into searches per 100,000 inhabitants and categorized qualitatively. Results: A total search volume of 7405 searches per 100,000 inhabitants in Germany and 17,592 searches per 100,000 inhabitants in Sweden was observed, with the total yearly search volume increasing continually in both countries during the study period. Regional search volume correlated with antihistamine dispensation rates (ρ = 0.848–0.960) and pollen concentration (ρ = 0.566–0.922). While overall search interest was higher in Sweden, a higher interest in treatment options was identified in Germany. Conclusion: Internet websearch data is an excellent proxy for disease activity of allergic rhinitis. In the 4-year study period, the interest in pollen allergies has increased and there are unmet medical needs in both countries