Introduction
smell complaints, ’, loss of smell, traumatic, Loss of smell, olfactory loss, smell loss, idiopathic smell disorders
OLFACTORY DISORDER, RESPIRATORY VIRAL INFECTION
At the time of writing (July 9th, 2023), there have been more than 676 million confirmed cases of COVID-19 worldwide.Loss of smell is a very common symptom in COVID-19. It affected between 64.76% and 67.49% patients included in a cohort tracking of self-reported symptoms in United States and United Kingdom.One year later, a Brazilian group confirmed the high prevalence of olfactory disorders in patients with early COVID-19. According to Brandão Neto et al., 65.1% of COVID-19 patients had smell complaints.Since the pandemic started, the knowledge about loss of smell due to COVID-19 has been increased. Before pandemic, there was some therapies used to recover loss of smell. Alpha-lipoic acidAlpha-lipoic acid (ALA) is a fatty acid that presents antioxidative effects, and neuronal regenerative capabilities. Accordingly, Hummel et al. showed that 61% of patients with smell loss after upper respiratory viral infection has improved olfactory function using 600 mg/day of ALA, for an average period of 4.5-months.In a later study, the same work group has shown an increase of olfactory function in patients who performed a 12-week olfactory training protocol twice a day to four intense odorants (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon and eugenol: cloves). That study included postinfectious, post traumatic and idiopathic smell disorders’ patients, and evaluated Sniff and Stick’s test results.There is enough literature regarding olfactory training to recover olfactory loss due to COVID-19. As an example, Pires et al. showed significant olfactory improvement in patients with smell loss due to COVID-19 receiving OT with 4 or 8 essences after 4 weeks.The aim of this study is to assess the effect of alpha-lipoic acid as an adjuvant of Olfactory Training (OT) on the improvement of smell loss in post-COVID-19 patients.