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Authors: Valentin Navel, Frédéric Chiambaretta, Frédéric Dutheil
Journal: Journal of Allergy and Clinical Immunology (2020)

We read with interest the relevant comment of Gallo et al1Gallo O. Bruno C. Locatello L.G. Global lockdown, pollution, and respiratory allergic disease: are we in or are we out?.J Allergy Clin Immunol. 2020; 146: 542-544Abstract Full Text Full Text PDF Scopus (8) Google Scholar concerning our recent Editorial.2Navel V. Chiambaretta F. Dutheil F. Will environmental impacts of social distancing due to the SARS-CoV-2 pandemic decrease allergic disease?.J Allergy Clin Immunol. 2020; 146: 70-71Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Globally, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has upset the lifestyle of humans, increasing sedentary behaviors with quarantine (ie, staying at home, tele-working, screen activities), the fear of contagion (ie, social connections, mass transit, and compulsive disinfecting), and probably a city dweller migration to the periphery of crowed cities and surrounding countryside. As explained by the authors, this exceptional period seems to be salient to explore the complex interplay of interactions between exposome (ie, indoor and outdoor expositions), genetic heritage, lifestyle, and allergic diseases expression. Interestingly, more than half the people stayed at home to prevent the spreading of SARS-CoV-2 during the several months of quarantine, involving a massive decrease in greenhouse gas emissions related to human activities. Considering the irritative factor of air pollution for the respiratory tract, the eyes, and the skin, we could attempt a reduction in allergic exacerbations mediated by nonspecific inflammation. Considering that filtering face piece respirators (FFPs) reduced the penetration of fine particulates ranging from 80% (FFP1) to 99% (FFP3), their global use during the coronavirus disease 2019 pandemic could protect people against outdoor and indoor allergenic components.3Jung H. Kim J.K. Lee S. Lee J. Kim J. Tsai P. et al.Comparison of filtration efficiency and pressure drop in anti-yellow sand masks, quarantine masks, medical masks, general masks, and handkerchiefs.Aerosol Air Qual Res. 2014; 14: 991-1002Crossref Scopus (99) Google Scholar However, the authors rightly highlighted that people were particularly exposed to biological aeroallergens (ie, dust mites, domestic animals, or molds) and chemical components (ie, ammonia, solvent, tobacco, and cooking smokes) of home indoor environment during quarantine. Similar to the concentration of diesel exhaust particles in a vehicle cabin exposed to heavy traffic, nonventilated houses could condense the toxicity of outdoor air pollution during several days. During the past decades, some countries have developed models of energy other than petroleum to promote more renewable energy sources, that is, wave power, offshore wind power, photovoltaic, or wood. However, it is widely accepted that home exposure to wood smoke causes inflammation in the respiratory system.4Rokoff L.B. Koutrakis P. Garshick E. Karagas M.R. Oken E. Gold D.R. et al.Wood stove pollution in the developed world: a case to raise awareness among pediatricians.Curr Problems Pediatr Adolesc Health Care. 2017; 47: 123-141Crossref PubMed Scopus (34) Google Scholar Promoting warm and humid environment, indoor activities (ie, tele-working, cooking, and indoor sports) could improve the exposition of airborne fungal spores in damp houses, increasing the incidence of asthma and allergic diseases.5Garrett M.H. Rayment P.R. Hooper M.A. Abramson M.J. Hooper B.M. Indoor airborne fungal spores, house dampness and associations with environmental factors and respiratory health in children.Clin Exp Allergy. 1998; 28: 459-467Crossref PubMed Scopus (365) Google Scholar Outdoor sports practice being prohibited, some people could run or cycle in their home. Moreover, evidence data showed that air pollutant exposure during exercise could decrease the pulmonary and vascular function in healthy individuals, increasing systemic and airways inflammation and amplifying the dose of pollutants during endurance physical activity.6Zhang J. Zhu T. Kipen H. Wang G. Huang W. Rich D. et al.Cardiorespiratory biomarker responses in healthy young adults to drastic air quality changes surrounding the 2008 Beijing Olympics.Res Rep Health Eff Inst. 2013; : 5-174Google Scholar Thus, the benefit of the decrease in air pollution could be attenuated by the massive exposure to indoor pollutants, aggravated by the toxicity of disinfectants such as bleach, rubbing alcohol, or quaternary ammonium—massively used to limit the spreading of SARS-CoV-2. Considering that the Hygienic Hypothesis highlighted the major role of microbiome to regulate the immune response to allergens, it would be very interesting to evaluate the impact of the extensive use of hygienic measures on the incidence of allergic diseases.7Weber J. Illi S. Nowak D. Schierl R. Holst O. von Mutius E. et al.Asthma and the hygiene hypothesis: does cleanliness matter?.Am J Respir Crit Care Med. 2015; 191: 522-529Crossref PubMed Scopus (54) Google Scholar Because of the fear of contagion, people may avoid mass transit and increase their commuting by individual car, which may in turn promote air pollution—and the release of the highly allergenic fine particulate matter. We may therefore see a bimodal response: a decrease in air pollution during the confined period, followed by an increase in air pollution—concomitantly with the effort of worldwide governments to kickstart economic growth (despite ecological engagements). To conclude, it will be salient to analyze the aforementioned factors related to allergic diseases in forthcoming months, to better understand the complex relation between allergens, air pollution, immune response, and exacerbation of allergic diseases. Global lockdown, pollution, and respiratory allergic diseases: Are we in or are we out?Journal of Allergy and Clinical ImmunologyVol. 146Issue 3PreviewWe have read with great interest the work by Navel et al1 about the impact of the current coronavirus disease 2019 pandemic on the burden of allergic diseases. The authors suggest that, thanks to the global lockdown of the majority of human industrial activities, the substantial reduction in air pollution in the urban areas, a well-known inducer of nonspecific airway inflammation, may have a positive effect on seasonal allergic diseases.1 Indeed, we are now facing a unique chance to decipher some of the complex interplays between the outdoor allergens, the air quality, and respiratory allergic diseases but, in order to have a full picture, we believe more (f)actors are needed on the stage. Full-Text PDF