Olfactory Dysfunction in Patients with Coronavirus Disease 2019: A Narrative Review

Background: The global public health and economic systems have been severely damaged by the coronavirus disease 2019 (COVID-19) pandemic. Olfactory dysfunction (OD) is one of the most prevalent symptoms experienced by COVID-19 patients, documented in clinical practice. In some individuals, OD is the first or the sole clinical symptom. In this review, the clinical characteristics, causes, evaluation procedures, prognosis, and available treatments of COVID-19-induced OD were examined. Methods: The PubMed, Scopus, Web of Sciences, and Google Scholar databases were searched for the related articles from inception until August 2022. Results: OD appears to be common in COVID-19, particularly in younger individuals and women and those with milder disease. Even though the issue is still unresolved, current research suggests that COVID-19-related OD is not caused by direct injury to olfactory sensory neurons but instead is a result of indirect injury to these cells. Moreover, effective therapeutic methods are inadequate despite the high prevalence of COVID-19-related OD. Conclusion: The focus of medical practice regarding COVID-19-related OD should be on identifying individuals with a poor prognosis who may benefit from early management to prevent complications, e.g., depression and anxiety, because COVID-19 OD generally has a good prognosis and quick recovery time.