IL5 and chronic rhinosinusitis: <b>Background:</b> The anti-IL-5 monoclonal antibody, mepolizumab, has shown clinical efficacy and safety for the treatment of severe eosinophilic asthma (SEA), chronic rhinosinusitis with nasal polyps (CRwNP) and eosinophilic granulomatosis with polyangiitis (EGPA).