The Efficacy of Intranasal Insulin in the Treatment of Post-Viral Persistent Olfactory Dysfunction: A Systematic Review.

objectivesThis study aimed to evaluate the therapeutic efficacy of intranasal insulin in treating persistent and refractory olfactory dysfunction following viral infections.

methodsA comprehensive literature search was performed across PubMed, Scopus, Embase, Web of Science, Google Scholar, and the Cochrane Library, covering all articles indexed up to July 2025. Studies were included if they evaluated changes in olfactory scores in patients receiving intranasal insulin, either compared with a control group (placebo or no treatment) or between pre- and post-treatment measurements. Secondary outcomes included serum glucose and insulin levels and the proportion of patients achieving significant olfactory recovery.

resultsEight studies including 457 participants were reviewed. Intranasal insulin was generally associated with improvement in olfactory scores. Delivery via absorbable materials may enhance both threshold and discrimination outcomes, whereas self-administration demonstrated minimal benefit. Several studies also reported higher rates of substantial olfactory recovery with absorbable material-based delivery. Combination therapy with intranasal insulin and budesonide was suggested to further improve threshold scores. Overall, treatment was well tolerated, with no major changes in serum glucose levels, although one study documented a mild hypoglycemic event.

conclusionCurrent evidence suggests that intranasal insulin, particularly when delivered using absorbable materials, may offer therapeutic benefit for persistent post-viral olfactory dysfunction. Corticosteroid coadministration may also provide additional improvements. These findings remain preliminary and require confirmation in larger, well-controlled studies.