The farm effect on asthma and allergies – Thirty years of research – Psychiatry AI: Real-Time AI Scoping Review

AI Summary

Farm exposure consistently protects against asthma and allergies worldwide, reflecting traditional lifestyle exposures humans experienced since the Neolithic.
High microbial load and diversity in animal sheds and unprocessed cow's milk promote immune maturation and underlie the protective farm effect.
Research progressed from epidemiology to biomarkers, microbiome sequencing and multi-omics, enabling translation into prevention strategies and emerging therapeutic interventions.

TL;DR (AI Generated)

The 'farm effect' describes a strong asthma- and allergy-protective signal by farm exposure, which is surprisingly consistent across the globe.

The aim of this review article is to delineate how research into the farm effect evolved from classical epidemiology over biomarker research, microbiome sequencing, and multi-omics analyses to emerging prevention strategies.

The decades of research into the farm effect represent true translational work: Moving from observation to intervention, with the advent of new therapeutic interventions on the horizon, now is the time to look back at how it all started, how our understanding has evolved over time and what this might mean for the future.

Basic summary

J Allergy Clin Immunol. 2026 Nov 13:S0091-6749(26)00803-1. doi: 10.1016/j.jaci.2026.10.027. Online ahead of print.

ABSTRACT

The ‘farm effect’ describes a strong asthma- and allergy-protective signal by farm exposure, which is surprisingly consistent across the globe. Representing a more traditional lifestyle, the farm environment appears to be a reminiscent of the environmental exposure humankind experienced since the neolithic. The farm environment is characterized by a high microbial load and diversity, which seem essential for adequate immune maturation. The aim of this review article is to delineate how research into the farm effect evolved from classical epidemiology over biomarker research, microbiome sequencing, and multi-omics analyses to emerging prevention strategies. We explore how the farm effect and the various versions of the hygiene hypothesis are closely intertwined with each simultaneously contributing the development of the other. We follow the development of our understanding of the mechanisms underpinning the farm effect, focusing on the two most consistent exposures, namely microbial exposure in animal sheds and consumption of unprocessed cow’s milk. The decades of research into the farm effect represent true translational work: Moving from observation to intervention, with the advent of new therapeutic interventions on the horizon, now is the time to look back at how it all started, how our understanding has evolved over time and what this might mean for the future.

PMID:43025765 | DOI:10.1016/j.jaci.2026.10.027

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