The clinical implications of the microbiome in the development of allergy diseases.

: A substantial number of patients worldwide are affected by allergies. Emerging evidence suggests that the individual microbial composition might contribute to the development of allergies or might even protect from allergic diseases.: This review provides a detailed summary regarding available knowledge on the composition of a healthy human microbiome at allergy relevant body sites. It highlights factors influencing the microbiota composition. Furthermore, recent findings on the mutual interaction of the microbiota with the innate and adaptive immune system are reported. In the final part, this knowledge is combined to discuss microbial implications for food allergy, allergic asthma, allergic rhinitis, and skin allergies. Literature for this review was gathered by searching PubMed and Google Scholar databases between October and December 2020.: Due to the highly individual composition, it is currently not possible to define the characteristics of a site-specific microbiome in health and disease. Mainly effects of bacterial communities have been investigated, while fungal or viral influences are not yet well understood. The communication between microbial communities found in different organs impact on allergy development. Thus, a personalized approach is essential to beneficially influence these complex interactions and to modulate the host-specific microbiota in allergies.