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Personalized essential oils may help people recover their lost sense of smell due to COVID-19, according to a new study.
Called olfactory training, the process involves smelling the oils regularly to “challenge” the nerves responsible for sending smell messages to the brain, according to The Mayo Clinic. Those nerves are known to be able to heal and regrow in a process called neuroplasticity.
The study was published last week in JAMA Otolaryngology-Head & Neck Surgery. It 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.
A traditional olfactory training protocol uses four specific scents: rose, lemon, eucalyptus, and clove. One group in the new study used those scents, while another group sniffed four scents that they selected themselves from 24 scent options. A third control group did not participate in olfactory training. Additionally, a subset of people in the study were shown images of the scents they smelled.
While there were no “definitive” differences between the individual approaches, the researchers noted that there may be benefits for patients who get to both select their scents and see images of the scents.
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.
“Allowing patients to select their own odorants may improve cost-effectiveness and increase adherence, particularly if there was an issue of familiarity with 1 of the classic 4 odorants,” she wrote. “The addition of visual cues to [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.”
An estimated 700,000 people have lost their sense of smell due to COVID-19, the authors said. Most people regain their sense of smell within a year.
The Mayo Clinic: “Olfactory retraining after COVID-19.”
JAMA Otolaryngology-Head & Neck Surgery: “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?”
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