The External Exposome and Food Allergy: How Environmental Exposures Shape Disease Risk.

IgE-mediated food allergy is a global health issue with rising prevalence that cannot be explained by genetic change alone, strongly suggesting that environmental exposures are a key driver. The external exposome encompasses several exposures that influence the developing immune system and modify food allergy risk. Environmental exposure to food allergens in household dust is increasingly recognized as a risk factor for sensitization, whereas early oral introduction promotes tolerance. Early-life microbial exposures, especially those associated with rural and farming environments, may protect against food allergies by stimulating innate immune pathways and shaping the gut microbiome. Co-exposures to microbial adjuvants can further alter risk in a timing-dependent manner. Epidemiological birth cohort studies have linked exposure to air pollutants, such as particulate matter and nitrogen dioxide, to food sensitization and allergy. Synthetic chemicals represent an emerging risk factor by disrupting epithelial barrier integrity and immune regulation. Ultra-processed food consumption and dietary additives may further increase risk by altering gut permeability and immune function. Significant gaps remain in our understanding of the most relevant environmental exposures affecting food allergy risk. Future research using longitudinal cohort designs and exposome-wide approaches is essential for developing evidence-based strategies to prevent food allergy.