The pathophysiological process underlying asthma and CRSwNP is mostly driven by shared inflammatory mechanisms, which involve a complex activation of innate and adaptive immune cells, and increased production of several pro-inflammatory cytokines (e.g., interleukin (IL)-4, IL-5, IL-13, thymic stromal lymphopoietin (TSLP)). Here, IL4 is linked to chronic rhinosinusitis with nasal polyps.