Back to beginnings of farming for answers to protection against allergies and atopy

On behalf of the GABRIEL Advanced Studies Group supported by the European Commission, Illi et al. (J Allergy Clin Immunol 2012;129:1470-1477) provide their results from a survey study designed to address the high variability in reported protective effects associated with farm environments on asthma and allergies (pp#). The study group survey was structured into two phases with questions in phase II targeting exposure to specific elements of the farm environment. Farms were placed in one of three categories depending on farm activities and husbandry: farms with no dairy cows or cattle, but other farm animals, and grain cultivation, farms with dairy cows and/or cattle, but no grain cultivation, and finally, farms with dairy cows and/or cattle, and grain cultivation. Survey queries covered exposure in utero to 3 years.

Illi et al. report that protective effects were highest and most broad for children raised on farms with both cows and cattle and agriculture activities. Exposure to cows, cows’ milk and straw had the greatest protective effect for asthma, exposure to fodder storage and manure were most protective on atopic dermatitis. Interestingly, the data collected could not sufficiently account for the protective effect against hay fever and atopic sensitization. Overall single exposure effect was greatest with cows’ milk, which greatly reduced the risk of asthma, hay fever and atopic sensitization. Exposure to straw had the strongest association with asthma protection, though the authors noted that the effects of individual constituents and contaminants in straw, such as manure, grass pollen, and microbial elements, could not be separated out.

Illi et al. comment that protective associations supported different physiological pathways, noting that cow exposure was associated with respiratory disease protection and cows’ milk association with atopic sensitization pointed to gut-mediated immune development.

The authors conclude that traditional farming environments like those established in humankind’s first non-nomadic lifestyle are the most beneficial from an immunologic natural history perspective. This can account for the variability in farm environment results since farming practices diverge greatly between the US and Central Europe.