Classical Olfactory Training for Smell Restoration: A Systematic Review

Olfactory dysfunction is commonly treated with olfactory training, but there is a lack of standardization in its methods, leading to inconclusive results about its effectiveness. This systematic review aims to investigate the effectiveness of classical olfactory training in the treatment of olfactory dysfunction compared to modified training or no-intervention control groups.

This systematic literature review follows the PRISMA protocol and is registered with PROSPERO (CRD42022357528). The databases used for the search were PubMed MEDLINE, LILACS, Scopus, Web of Science, and Embase. Randomized clinical trials carried out in adults with olfactory disorders and published in all languages until December 2023 were included. The quality assessment of these studies was conducted using the Cochrane Risk of Bias tool.

A total of eight studies, involving 896 participants with olfactory dysfunction, were included in the analysis. Overall, these studies showed that classical olfactory training produces improvements in at least 20%-30% in olfactory function in patients affected by different etiologies of smell loss, with all of them reporting clinically significant post-treatment results.

Classical olfactory training can be a promising intervention for the recovery of olfactory function in individuals with olfactory dysfunction. However, olfactory training should not be seen as a universal solution for anosmia, given the variability of results.