Course of Smell Disorders in COVID-19 Compared to Patients with Postinfectious Smell Loss Unrelated to COVID-19

Background: Olfactory dysfunction is a common symptom of viral upper respiratory tract infections (URTIs) and gained particular attention during the COVID-19 pandemic. Although COVID-19-associated smell loss is often reported as severe in the acute phase, its long-term trajectory compared to non-COVID-19 post-viral olfactory disorders is unclear, especially with psychophysical testing.

Methods: This longitudinal study examined the olfactory dysfunction following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection compared with olfactory impairment after other viral infections. Participants (n = 234) presenting with URTI and smell loss were assigned to a COVID-19 (C) or non-COVID-19 (nC) group based on reverse transcription polymerase chain reaction (RT-PCR) results. Follow-up assessments were conducted at 2 visits over a period of up to 21 months using questionnaires, Visual Analog Scales, and psychophysical evaluation with the extended Sniffin’ Sticks test assessing odor threshold, discrimination, and identification (Threshold Discrimination Identification [TDI] score).

Results: Acute-phase self-reports showed more severe olfactory loss in the C group versus the nC group. Over time, both groups subjectively recovered, with approximately 80% of participants reporting full restoration by the second follow-up visit (around 16 months post-infection). Threshold Discrimination Identification testing revealed no significant group differences at either follow-up, and recovery trajectories were comparable. Based on TDI scores, about half of participants in both groups remained hyposmic at the second follow-up despite self-perceived normalization of smell function.

Conclusion: Although COVID-19-related smell loss proves more intense acutely, its long-term progression does not differ significantly from other post-viral smell disorders. Patients often fail to notice mild smell loss on their own, making psychophysical tests like TDI essential for proper follow-up and counseling.

Cite this article as: Rubić L, Ressel C, Hummel T, Haehner A. Course of smell disorders in COVID-19 compared to patients with postinfectious smell loss unrelated to COVID-19. Balkan ORL-HNS. 2026, 3, 0141, doi: 10.5152/bohns.2026.26141.