Environmental protection from allergic diseases: From humans to mice and back

•Traditional farming represents one of the strongest 'asthma/allergy-protective' environments.•Environments with high biodiversity, and pets at home (dogs) also show strong protection.•A strong association between allergy protection and environmental and/or host microbiota is apparent.•Reduced biodiversity adversely affects commensal microbiota and subsequent immunoregulation.•Mechanisms of allergy-protection via microbiota involve innate and adaptive immunity.

Allergic diseases have a strong environmental component, illustrated by the rapid rise of their prevalence in the Western world. Environmental exposures have been consistently shown to either promote or protect against allergic disease. Here we focus on protective exposures and the pathways they regulate. Traditional farming, natural environments with high biodiversity, and pets in the home (particularly dogs) have the most potent and consistent allergy-protective effects and are actively investigated to identify the environmental and host-based factors that confer allergy protection. Recent work emphasizes the critical protective role of microbial diversity and its interactions with the gut/lung and skin/lung axes - a cross-talk through which microbial exposure in the gut or skin powerfully influences immune responses in the lung.