Impact of Climate Change-Related Environmental Factors on Allergen Production and the Epidemiology and Severity of Allergic Diseases.

Background: Allergic disease affects up to 40% of the adult population worldwide. This percentage is increasing as a result of environmental changes related to global warming.

Methods: We undertook a systematic review of the literature to identify and evaluate current evidence on the impact of climate change-related environmental factors on allergen production and the epidemiology and severity of allergic diseases. We applied the Population, Exposure, Comparison, Outcome (PECO) criteria to guide our literature searches of the PubMed and Cochrane databases (January 1, 2016 to December 31, 2021). Study outcomes were categorized and grouped to facilitate data synthesis. Outcomes were classified as significant (P<.05), nonsignificant (P>.05), or undetermined (P value not reported). Study quality was assessed using the Mixed Methods Appraisal Tool.

Results: Of 195 studies, 40 were considered relevant, and 9 provided data that could be included in the quantitative data synthesis. Environmental factors, including the presence of pollutants, temperature, and drought influenced the type, volume, and timing of exposure to local aeroallergens. The most relevant environmental factor was the presence of environmental pollutants, of which tropospheric ozone was the most frequently associated with changes in allergen production and prevalence and severity of allergic disease. Several publications also demonstrated the impact of environmental factors on health care burden.

Conclusions: Climate change-related environmental factors worsened allergic disease in terms of prevalence, severity, and health care burden owing to alterations in allergen exposure (volume and type), with the presence of pollutants such as ozone being the most common drivers of this increase.