IL-5 is a cytokine that plays a crucial role in the activation, differentiation, chemotaxis, and survival of eosinophils.42, 43 As IL-4 and IL-13, IL-5 is a typical marker of type 2 inflammatory response and is increased in a significant proportion of patients with CRSwNP. This evidence concerns the gene IL13 and chronic rhinosinusitis with nasal polyps.