Although allergies exist everywhere, rates vary drastically from country to country. There is a clear link, however, between urban and Western societies and an increased prevalence of allergies and asthma.
Why is this?
Scientists theorize that it’s due to several factors:
The microbiome hypothesis
The microbiome hypothesis suggests that (1) reduced exposure to certain infections and microbial agents and (2) higher rates of antibiotic use during childhood may lead to an increased risk of allergic conditions like asthma. Western societies have an emphasis on cleanliness which may lead to lower exposure to certain beneficial microbes, potentially leading to an increased risk of allergic rhinitis and asthma.
Lifestyle and diet
Western countries have experienced changes in lifestyle patterns, including dietary changes and reduced physical activity. These factors may contribute to an increased risk of asthma and allergies. For example, a diet high in processed foods and low in fruits and vegetables has been associated with a higher risk of asthma development.
Indoor air quality
Recent data shows that gas stoves lead to worsening air quality at home and can make symptoms worse for asthma patients (https://www.health.harvard.edu/blog/have-a-gas-stove-how-to-reduce-pollution-that-may-harm-health-202209072811). One analysis of observational research found that children living in households that use gas stoves for cooking are 42% more likely to have asthma.
Urbanization has led to larger numbers of children and adults having significant exposure to pollution, which can worsen respiratory symptoms and increase the risk of allergic conditions. Exposure to pollutants such as particulate matter, nitrogen dioxide, and ozone has been linked to the development and exacerbation of asthma.
It is crucial to recognize that the prevalence of allergic asthma can vary within Western countries and can also be influenced by factors beyond the ones mentioned above, such as access to healthcare, socioeconomic status, and cultural practices.
(1) Okada, H et al. “The 'hygiene hypothesis' for autoimmune and allergic diseases: an update (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841828/).” Clinical and experimental immunology vol. 160,1 (2010): 1-9. doi:10.1111/j.1365-2249.2010.04139.x
(2) Frontela-Saseta, Carmen et al. “Diet: A Specific Part of the Western Lifestyle Pack in the Asthma Epidemic (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7408793/#:~:text=In%20the%20case%20of%20the,key%20role%20in%20asthma%20patients.).” Journal of clinical medicine vol. 9,7 2063. 1 Jul. 2020, doi:10.3390/jcm9072063
(3) Lin, Weiwei, et al. "Meta-Analysis of the Effects of Indoor Nitrogen Dioxide and Gas Cooking on Asthma and Wheeze in Children (https://academic.oup.com/ije/article/42/6/1724/737113?login=false)." International Journal of Epidemiology, vol. 42, no. 6, 2013, pp. 1724-1737, https://doi.org/10.1093/ije/dyt150. Accessed 30 May 2023.
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