The Microbiome, Timing, and Barrier Function in the Context of Allergic Disease.

Allergic disease affects millions. Despite many advances in our understanding of the immune system in the past century, the physiologic underpinning for the existence of allergy remains largely mysterious. Food allergies, in particular, have increased dramatically in recent years, adding a new sense of urgency to unraveling this mystery. The concurrence of significant lifestyle changes in Western societies with increasing disease prevalence implies a causal link. Demographic variables that influence the composition and function of the commensal microbiota early in life seem to be most important. Identifying the evolutionary and physiologic foundations of allergic disease and defining what about our modern environment is responsible for its increased incidence will provide insights critical to the development of new approaches to prevention and treatment.