Clinical efficacy of olfactory training using aromatic traditional Chinese medicine in managing olfactory dysfunction induced by SARS-CoV-2

Objective: The aim of this study is to assess the clinical efficacy of olfactory training using aromatic traditional Chinese medicine (TCM) for addressing severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-induced olfactory dysfunction, while also exploring the factors that influence the observed efficacy. Methods: 172 outpatients with SARS-CoV-2-related olfactory dysfunction were randomized into two groups. The experimental group received olfactory training with TCM aromatics (ginger, Pericarpium Citri Reticulatae, Santali Albi Lignum, Styrax), while the control group used non-TCM aromatics (phenyl ethanol-rose, menthol-mint, citronellal-lemon, eugenol-clove) for 24 weeks. Olfactory function was assessed using the Sniffin' Sticks test and TDI (threshold-discrimination-identification) scores at baseline, 1, 3, and 6 months post-treatment. Results: Response rates at 1, 3, and 6 months post-treatment were 3.66%, 25.61%, and 43.90% in the experimental group, and 4.94%, 23.46%, and 43.21% in the control group. The TDI scores of the experimental group and the control group were statistically different before and after treatment. At 3 and 6 months post-treatment, TDI scores increased significantly, with enhanced odor discrimination and identification capabilities in both groups compared to pre-treatment, while the odor detection threshold was not improved compared with that before treatment. At the 3- and 6-month follow-ups, experimental group showed significantly higher self-rated sleep and anxiety scores than controls, indicating notable improvement in both after treatment. Conclusion: Olfactory training with aromatic TCM offers an effective treatment for SARS-CoV-2-induced olfactory dysfunction, improving odor discrimination, identification without significant differences compared to conventional aromatics, besides, it may also improve anxiety and sleep quality.