The reasons for dual therapy were the following: 3 patients had persistent hypereosinophilia during dupilumab, 2 patients developed hypereosinophilic syndrome (HES) when treated with dupilumab but had insufficient control of CRSwNP when treated with anti-IL5 only, 1 patient had insufficient control of asthma on dupilumab only and insufficient control of CRSwNP when on anti-IL5 treatment only, and 1 patient developed a side effect (arthritis) possibly related to dupilumab but had insufficient control of CRSwNP on anti-IL5 only after dupilumab discontinuation. This evidence concerns the gene IL5 and chronic rhinosinusitis with nasal polyps.