Background: Impairment of smell is more commonly related to chronic rhinosinusitis with nasal polyps (CRSwNP) than without, especially when asthma and/or NSAID-exacerbated respiratory disease and type 2 inflammation are also present. Therapeutic options include intranasal and systemic corticosteroids, surgery, and, more recently, biological therapy. We summarize current knowledge on the effect of biologics on olfaction in patients with CRSwNP.
Methods: We performed a systematic search of the PubMed and Cochrane databases from January 2001 to June 2022. The inclusion criteria were as follows: adult patients with CRS treated with dupilumab, omalizumab, mepolizumab, benralizumab, or reslizumab; and studies published in English reporting outcomes for sense of smell based on psychophysical and/or subjective tools. We excluded reports that did not assess CRSwNP, loss of smell evaluated with a method other than those accepted in the inclusion criteria, review articles, and expert opinions. No funding was received.
Results: Dupilumab has demonstrated rapid and sustained long-term improvement in smell in clinical trials and in real life. Omalizumab improves smell at 24 weeks. This improvement is maintained in the long-term, although it is not clinically relevant. Mepolizumab and benralizumab improved smell in the long term based on a subjective scale. No studies examining the improvement in smell in patients with CRSwNP treated with reslizumab were found. Indirect comparisons by meta-analysis consistently conclude that dupilumab is the most effective biologic for improving impaired sense of smell.
Conclusion: Dupilumab seems to be more efficacious for improving the sense of smell than omalizumab, mepolizumab, and benralizumab.

Key words: Smell, Chronic rhinosinusitis with nasal polyps (CRSwNP), Dupilumab, Omalizumab, Mepolizumab, Benralizumab, Monoclonal antibodies