Since CRS is characterized by different pheno- and endotypes (3, 6, 7), we studied the microbiome in relation to various relevant features describing phenotypes (i.e., asthma, allergy, polyps, and infection) and inflammatory markers (i.e., periostin, interleukin-4 [IL-4], IL-13, IL-5, and interferon gamma [IFN-γ]). This evidence concerns the gene IL13 and allergic disease.