Olfactory training with essential oils for patients with post-COVID-19 smell dysfunction: A case series

INTRODUCTION: It is estimated that up to one third of COVID-19 patients can develop long-lasting smell dysfunction. Viral infections, especially COVID-19, can cause anosmia through different pathomechanisms, and different strategies have been proposed for effectively managing post-COVID-19 olfactory dysfunction in clinical practice, with olfactory training being recommended as a first-line treatment option. METHODS: This report describes a non-consecutive series of clinical cases. After COVID-19, eight cases (5 females, 3 males) of adult patients with long-lasting (3+ months) post-viral smell dysfunction followed a 30-day olfactory training protocol with a set of plant-derived essential oils. At baseline and at the end of the treatment, the patients were administered the Assessment of Self-reported Olfactory Functioning (ASOF) questionnaire, an inventory used to measure olfactory dysfunction and health-related quality of life. RESULTS: For any of the outcomes assessed with the ASOF scale, a significant improvement from baseline was reported, even though mean value ameliorations were more pronounced for olfactory function per se (Subjective Olfactory Capability: from 3.6 to 5.6 out of 10; Self-Reported capability of Perceiving specific odors: from 1.8 to 3.0 out of 5), rather than for health-related quality of life (Olfactory-Related Quality of life: from 2.9 to 3.9 out of 6). CONCLUSIONS: It was observed that patients with long-lasting COVID-19-related smell dysfunction improved after a 30-day olfactory training protocol. Further controlled clinical studies would be useful to better investigate the role of olfactory training in patients with postviral smell dysfunction.