Climate Change-Associated Environmental Factors and Pollutants: Impact on Allergic Diseases, Epidemiology, Severity, and Health Care Burden.

Allergic diseases affect up to 40% of adults worldwide, a percentage that is increasing with environmental changes related to global warming. A systematic review of the literature was performed to identify and evaluate current evidence of the effect of climate change-related environmental factors on the prevalence, incidence, and severity of allergic diseases in terms of the impact on patients with allergy. PECO criteria for 2 research questions were established and guided the 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). Assessment of the 2 questions enabled us to identify 609 publications. Of these, 96 were assessed for eligibility and 42 provided data. Environmental factors, including the presence of pollutants, influenced patients' conditions in terms of effects on allergy, exposure to allergen(s), and the immune system. The pollutants most frequently reported to have an impact were nitrogen dioxide (NO2) and particles <2.5 μm in diameter. The allergic diseases most frequently reported to be affected by environmental factors were respiratory disease (asthma and rhinitis) and atopic dermatitis, with an impact on epidemiology and health care burden. Environmental pollution increased the frequency and health care burden of allergic diseases. The effect of environmental pollution was predominantly caused by pollutants such as NO2 and particles <2.5 μm in diameter and was observed across allergic diseases, including respiratory disease (asthma and rhinitis) and atopic dermatitis.