IHC analysis of nasal mucosal tissue from CRS patients revealed the presence of IL4I1, AhR, and CYP1B1 in the human nasal epithelium (Figure 4C), with protein expression levels significantly higher in CRSwNP and CRSsNP compared with control (Figure 4D). This evidence concerns the gene IL4I1 and chronic rhinosinusitis without nasal polyps.