The interconnection between environment, immune-nutrition and allergic disease

The global prevalence of allergic diseases—including asthma, allergic rhinitis, atopic dermatitis, and food allergy—has reached epidemic proportions and now represents a major public health challenge [1]. This rise is particularly striking in Asia, the world’s most populous continent, which encompasses diverse cultures, lifestyles, environments, and genetic factors, which contribute to the unique characteristics of allergic diseases in this area. 1. Environment and allergies The rapid escalation of allergic and other immune-mediated non-communicable diseases (NCDs) cannot be explained by genetic factors alone. Instead, compelling epidemiological and experimental evidence implicates profound environmental changes associated with climate change, urbanization, air pollution, and biodiversity loss as central drivers of immune dysregulation [2,3]. Climate change and global warming have contributed to rising sea levels, extreme weather events, wildfires, and desertification. Vulnerable and those from low-income countries especially women and children, individuals with comorbidities, and the elderly are particularly susceptible to the impact of climate change. These environmental effects increase allergenic pollen like ragweed [4], increase allergen exposure and also alter host–microbe interactions and immune tolerance mechanisms. Reduced biodiversity—both at the ecosystem level and within the human microbiome—has emerged as a critical determinant of immune health. Studies in healthy populations and patients with chronic inflammatory diseases consistently demonstrate associations between diminished microbial diversity and conditions such as asthma, type 1 diabetes, inflammatory bowel disease, and obesity. Urbanization-related lifestyle changes, including reduced contact with natural environments and increased exposure to pollutants, are key contributors to these microbial alterations. Observations in immigrant populations further underscore this phenomenon, with rapid increases in allergic and autoimmune disease risk following migration from microbe-rich to microbe-poor environments. Mechanistically, these changes converge on innate immune pathways, particularly those involving pattern-recognition receptors such as Toll-like receptors (TLRs), notably TLR4. Physical activity, nutrition, environmental pollutants, and the microbiome interact to shape immune maturation and inflammatory responses. Metagenomic and immunological studies have demonstrated the pivotal role of the microbiota in regulating immune cell subsets relevant to allergic disease, including Th1, Th2, Th17, regulatory T cells, dendritic cells, and epithelial–immune singling networks. 2. Epithelial Barrier theory In this context, the Epithelial Barrier Theory provides a unifying framework to explain the parallel global rise in allergic, autoimmune, and chronic inflammatory diseases over the past six decades [5]. Industrialization and modernization have dramatically altered the human exposome, increasing exposure to chemical pollutants, detergents, microplastics, particulate matter, and food additives. These agents disrupt the integrity of epithelial barriers in the skin, respiratory tract, and gastrointestinal mucosa, facilitating translocation of harmful substances and microbes into subepithelial tissues. The resulting epithelial dysfunction, microbial dysbiosis, and chronic low-grade inflammation can initiate or exacerbate allergic and other immune-mediated diseases [5,6]. 3. Diet, diet diversity, ultraprocessed foods and Immune-nutrition Alongside environmental exposures, diet has emerged as a critical and modifiable determinant of immune development and allergic disease risk. Immune-nutrition—an interdisciplinary field examining interactions among dietary components, the microbiome, and immune function—offers a unifying framework linking nutrition, sustainability, and allergy prevention. Growing evidence indicates that diet quality, food diversity, and degree of food processing significantly influence immune tolerance and allergic outcomes. Within this framework, diet diversity, sustainable dietary patterns, and reduced consumption of ultraprocessed foods have emerged as critical and interrelated determinants of allergic disease risk and management [7,8]. A sustainable diet is commonly defined as one that promotes health and wellbeing while respecting environmental limits and preserving resources for future generations [7–9]. Sustainable eating practices emphasize increased consumption of plant-based foods, including vegetables, fruits, legumes, whole grains, nuts, and seeds. These foods are rich in dietary fiber, polyphenols, and micronutrients that support microbial diversity and the production of immunoregulatory metabolites such as short-chain fatty acids. In contrast, high reliance on resource-intensive animal products, particularly ruminant meats, is associated with increased greenhouse gas emissions and greater environmental burden [2,3]. Dietary diversity, particularly during early life, is a cornerstone of immune education. Exposure to a broad range of foods and bioactive compounds supports oral tolerance and balanced immune maturation. Observational studies consistently associate greater dietary diversity in infancy and childhood with reduced risk of food allergy, asthma, and atopic disease. Importantly, sustainability in nutrition should not be viewed as separate from clinical allergy care but rather as an extension of evidence-based dietary guidance that simultaneously benefits human and planetary health. Diet diversity is also a key driver of gut microbiome diversity. Microbial richness and functional capacity are influenced by the range of substrates available for fermentation, particularly complex carbohydrates and fibers. These microbial communities, in turn, shape immune maturation through effects on epithelial barrier function, regulatory T-cell development, and inflammatory signaling pathways. Sustainable, plant-forward diets inherently support dietary diversity and microbial resilience, reinforcing their relevance for allergy prevention and management that simultaneously address human and planetary health. Diet diversity is also a key driver of gut microbiome diversity. Microbial richness and functional capacity are influenced by the range of substrates available for fermentation, particularly complex carbohydrates and fibers. These microbial communities, in turn, shape immune maturation through effects on epithelial barrier function, regulatory T-cell development, and inflammatory signaling pathways. Sustainable, plant-forward diets inherently support dietary diversity and microbial resilience, reinforcing their relevance for allergy prevention and management. Food systems themselves are major contributors to greenhouse gas emissions, land degradation, water use, and biodiversity loss. While plant-forward dietary patterns generally confer lower environmental impact, sustainability cannot be inferred solely from whether a food is plant-based or allergen-free. Food processing, packaging, transportation, and waste all contribute meaningfully to environmental burden and, indirectly, to immune health. Ultraprocessed foods are defined using the NOVA classification system as industrial formulations composed largely or entirely of substances derived from foods, along with additives designed to enhance palatability, shelf life, and convenience [10,11]. These products often contain multiple ingredients rarely used in home cooking, such as refined starches, glucose syrups, emulsifiers, stabilizers, flavorings, and colorants. Additional sustainable practices—such as choosing seasonal and locally produced foods, minimizing food waste, and reducing single-use packaging—further contribute to environmental stewardship while reinforcing dietary quality [12]. 4. Conclusion The intersection of climate change, environmental degradation, immune-nutrition, and allergic disease represents a critical frontier in allergy research and clinical practice. Addressing these challenges requires coordinated action across clinical medicine, public health, environmental policy, and societal behavior. The G20, 2023 under India’s presidency and guided by the ethos “One Earth, One Family, One Future,” has emphasized the concept of “Lifestyle for Environment (LiFE).” The G20–T20 Task Force, 2023 on LiFE, Resilience, and Values for Wellbeing has advanced policy recommendations rooted in a one health framework, recognizing the interconnectedness of human, animal, and environmental health [6,13]. Beyond governmental initiatives, mitigation strategies must include reducing exposure to environmental pollutants, improving energy efficiency in buildings and transportation, promoting sustainable mobility, and strengthening public education and civil society engagement. The one health and planetary health frameworks underscore the necessity of multidisciplinary, cross-sectoral, and transnational collaboration to restore ecological balance and reduce the burden of allergic and immune-mediated diseases. Conflicts of interest The authors have no financial conflicts of interest. Author contributions Writing: Ruby Pawankar, Luo Zhang.