Olfactory training, also known as smell retraining therapy, is the process of smelling familiar odors to stimulate and re-engage the sense of smell. Over time as nerves regrow, smell training encourages improved brain connectivity by focusing on memories and experiences while you smell foods and scents. By a process known as neuroplasticity, those nerves are known to be able to recover and develop again.
The study included 275 people ages 18 to 71 who reported loss of smell due to COVID-19. Participants sniffed the oils for 15 seconds with a 30-second rest in between odors. The study lasted for 3 months (
One group in the study used the traditional olfactory training protocol which includes 4 scents. These are rose, lemon, eucalyptus, and clove.
Another group sniffed four scents that they selected themselves out of 24 scent options. A third control group did not participate in olfactory training. In addition, a subset of the participants in the study were shown photographs of the scents they smelled.
There were no ‘definitive’ differences between the individual ways. The researchers observed that there may be advantages for patients who get to choose their fragrances as well as see visuals of the odours.
In a companion commentary published with the study, Carol Yan, MD, of the University of California San Diego, said the improvements some patients saw may have been a placebo effect and should be considered for treatment plans of patients who lost their sense of smell due to COVID-19 (2✔ ✔Trusted Source
Assessing Efficacy Using Variations of Olfactory Training for COVID-19-Related Smell Loss-Would a Rose by Any Other Scent Smell as Strong?
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Allowing patients to select their own essential oils may improve cost-effectiveness and increase adherence. This is especially true if they were not familiar with 1 of the classic 4 odorants. The addition of visual cues to the olfactory training may improve engagement in some patients while increasing the burden on others. Ultimately, patients’ belief and satisfaction in their therapeutic plan can have substantial placebo-effect benefits that are not to be ignored.
Cause of Chronic Loss of Smell
The most common cause of chronic olfactory loss (OL) is post-viral olfactory dysfunction (PVOD), which accounts for 19% to 43% of all cases. As a result of the COVID-19 epidemic, an estimated 700,000 additional OL cases are expected. Olfactory loss has been associated to a variety of negative consequences, including depression onset, impaired detection of dangerous stimuli such as smoke and rotten foods, weight loss, poor social well-being, and higher mortality in older persons (3✔ ✔Trusted Source
Health-related and specific olfaction-related quality of life in patients with chronic functional anosmia or severe hyposmia
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Connection Between Smell and Vision
Dual-sensory stimulation training has been shown to enhance a variety of different sensory and cognitive processes, including auditory adaption process. Numerous studies have shown an intimate connection between olfaction and vision. Data suggest that multisensory integration through the addition of a visual component to OT may potentiate olfactory neuroplasticity by stimulating cross-modal sensory transfer. Previous studies have also demonstrated that OT protocols with modifications that increase adherence are associated with increased efficacy (4✔ ✔Trusted Source
Olfactory training ball improves adherence and olfactory outcomes in post-infectious olfactory dysfunction
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- Efficacy of Combined Visual-Olfactory Training With Patient-Preferred Scents as Treatment for Patients With COVID-19 Resultant Olfactory Loss
- Assessing Efficacy Using Variations of Olfactory Training for COVID-19-Related Smell Loss-Would a Rose by Any Other Scent Smell as Strong?
- Health-related and specific olfaction-related quality of life in patients with chronic functional anosmia or severe hyposmia
- Olfactory training ball improves adherence and olfactory outcomes in post-infectious olfactory dysfunction
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