Update on environmental determinants of allergic diseases

This review article summarizes key advances from October 2022 to December 2025 on the link between environmental exposures and allergic diseases, with an emphasis on early-life exposures and mechanistic insights relevant to disease prevention and therapy. Allergic diseases have genetic and environmental origins. As to the latter, predisposition to allergy is thought to arise as a result of increased exposure to harmful environmental factors that act as immune adjuvants for allergens, and reduced exposure to beneficial factors that induce allergen tolerance. Harmful factors include air pollutants (eg, road traffic-related particulate matter and gases, cigarette smoke, fire smoke), and various man-made chemicals and particles. Beneficial exposures include commensal microorganisms and nonmicrobial factors present in the farming environment. Allergic diseases frequently start in early childhood. Therefore, many recently published reports focus on environmental exposures occurring prenatally or during the first few months or years after birth-that is, time windows before allergic disease manifestation. This review article summarizes and comments on recent work on prenatal, childhood, adult, protective, and harmful exposures, highlighting relevant human cohort studies as well as mechanistic work in mouse models and in vitro culture systems. Studies published in the past 3 years describe novel biomarkers of environmental exposures, elucidate novel mechanisms by which exposures shape allergic diseases, and highlight novel targets for therapeutic intervention, setting a foundation for new approaches for early detection of allergic predisposition, allergy treatment, and prevention.