Reviews and feature articleExternal exposome and allergic respiratory and skin diseases
Section snippets
Specific external exposome
Allergens and air pollutants are well-established ubiquitous risk factors for allergic diseases. Everyone is exposed to a mixture of allergens and air pollutants, which changes many times a day, moving between indoor and outdoor spaces and urban and rural areas during different seasons of the year (Fig 2). Indoor environments are usually not hermetically sealed, and outdoor air and its content “contaminate” indoor spaces10; in addition, meteorological and indoor conditions affect concentrations
Climate
Among nonspecific factors, climate is of paramount importance for allergic diseases by acting on them directly or influencing their risk factors. Increases in the production and concentration of aeroallergens and chemical air pollutants and of their geographic distribution are due to changes in climate and weather patterns.
Interactions between aeroallergens and meteorological factors at a molecular level, and the immune system
Although studies on the effects of increased temperature and CO2 on distribution, phenology, and pollen production indicate some consistent trends for most plants producing allergenic pollen, data about the effects on allergen content of pollen (the so-called “molecular aerobiology”)66 are still in their infancy. The milestone in this field is the European Union–funded Health Impacts of Airborne Allergen Information Network (HIALINE) project that aimed at measuring the daily amount of pollen
The biodiversity hypothesis and role of the microbiome
Because known risk factors cannot explain the increase in the prevalence of allergic diseases worldwide, research has shifted toward other possible causes. Among these, biodiversity loss and climate change resulting from human activity have recently been evoked.92 Altered composition of the gut and skin microbiota is characteristic of various inflammatory conditions, including asthma and allergies.93, 94 Animal studies support the hypothesis that aberrations in the gut and skin microbiome might
Adaptation and mitigation actions to control external exposome
One of the major global challenges is the reduction in GHG emissions, some of which are also air pollutants. Both large- and small-scale interventions are needed to slow down the increase in GHG emissions, and both institutions and individuals are responsible.
Another objective involves controlling urban settings. Urbanization is on an upward trend, with 66% of the global population expected to be living in cities by 2050.99 Because extreme temperature events and air pollution are projected to
Conclusion
Substantial evidence indicates that a wide range of environmental risk factors and interactions contribute to allergic diseases, showing the relevance of considering the external exposome in the etiopathogenesis of these diseases. This should improve the comprehension of these conditions and open the way to adapted prevention strategies accounting for lifestyle and socioeconomic factors.
Research needs
Research to understand the effect of the external exposome is as crucial as strategies and policies to reduce emissions of GHGs and air pollution. The scientific community is responsible for both investigating the macromechanisms and micromechanisms of the effects of environmental changes on human health and tracking the indicators of effect, adaptation, and mitigation, as in the case of “the Lancet Countdown” initiative.107
Present and future environmental research on macromechanisms is bound
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2022, Immunology and Allergy Clinics of North AmericaCitation Excerpt :Recent epidemiologic and clinical studies suggest the involvement of external environmental influences in at least some individuals with EoE.4 The developing immune system is critically susceptible to external factors, and the emerging field of exposomics seeks to understand how lifetime environmental exposures affect health.5 Exposure to biologic and chemical insults such as allergen proteases, detergents, ozone, and particulate matter damages the epithelial barrier, potentially leading to chronic inflammation.6
This review was partially supported by the European Union FP7-ENV Health and Environment-wide Associations based on Large population Surveys (HEALS) project.
Disclosure of potential conflict of interest: The authors declare that they have no relevant conflicts of interest.
Terms in boldface and italics are detailed in the glossary on page 847.