Abstract Epidemiologic studies revealed a crucial role of the environment for the increased prevalence of allergic disorders. e microbiota as part of our immediate environment promotes immune diversity that facilitates a well-equilibrated balance between immunity and tolerance. Alterations of our symbiotic microbiota especially in early life is thought to play a fundamental role in dening susceptibility to the development of allergic diseases during adult life on the population level. Due to a high density of bacteria, viruses and fungi and a large contact surface area for host-microbiota interactions, the most relevant interaction between microbes and our immune system are thought to occur in the gut. e immune system co-evolved with the symbiotic microbiota and adopted a variety of mechanisms to allow a dynamic state of tolerance, including the induction of regulatory T cells (Tregs). Foxp3-expressing Tregs are welldescribed immune regulators in autoimmune and allergic disorders. However, recent years have shown that Tregs can come in di­erent €avours with di­erent regulatory potential and outcome for our immune system. is review summarizes novel ndings from basic immunology research that may help to better understand the interaction between the microbiota, di­erentiation of Tregs and its consequences for the onset and regulation of allergic disorders.