Olfactory Training for Post-COVID-19 Olfactory Dysfunction: A Meta-Analysis of Efficacy and Combination Therapies

Background/Objectives: This systematic review and meta-analysis evaluated the effectiveness of olfactory training (OT) using standardized protocols in patients with post-COVID-19 olfactory dysfunction. The objective was to assess whether OT, compared to no treatment, placebo, or alternative therapies, improved olfactory function as measured using validated smell tests, including UPSIT, Sniffin' Sticks (TDI score), CCCRC, and B-SIT. Methods: A systematic search of PubMed, Web of Science, and Ovid Medline was conducted through February 2025 in accordance with PRISMA guidelines. Eight randomized controlled trials (RCTs) met the inclusion criteria. Data were extracted on study characteristics (author, year, country, design, sample size), population details (age, sex, post-COVID-19 cause), intervention type (training method, frequency, duration), comparators, outcome measures (baseline and post-intervention olfactory scores), follow-up duration, and reported adverse effects. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal tool. Meta-analyses were performed using RevMan and Open Meta-Analyst. Results: Olfactory training significantly improved the olfactory scores compared to those of the controls. The greatest improvement was observed when OT was combined with PEA-luteolin (MD = 4.62, 95% CI: 2.17-7.06, p = 0.0002), followed by EDTA (MD = 2.33, 95% CI: 0.58-4.08, p = 0.009). Corticosteroids showed a borderline benefit (MD = 1.34, 95% CI: 0.01-2.67, p = 0.05), while alpha-lipoic acid had no significant effect. Combination therapies were associated with higher recovery rates (RR = 1.65, 95% CI: 1.13-2.42, p = 0.01). Conclusions: Olfactory training is an effective treatment for post-COVID-19 smell dysfunction. When paired with specific adjunct therapies, particularly PEA-luteolin, it may yield superior recovery outcomes. Further large-scale, standardized RCTs are needed to define optimal treatment protocols.