• Atoosa H. Bigvand

Olfactory Training: An Intervention for Post-COVID Smell Loss

Taste and smell loss have been included in the official list of symptoms of COVID.19. Olfactory Dysfunction (smell loss) has been reported in other viral infections (parainfluenza, rhinovirus, SARS, etc.), but the incidence is much lower than SARS-CoV-2 infection. “Evidence indicates that the prevalence of smell loss in COVID-19 patients is 48.85%.”

Olfactory dysfunction (OD), will negatively affect a patient's quality of life. Individuals with smell and taste loss encounter problems with cooking, decreased appetite, personal hygiene, social relationships, and emotional problems such as depression, feeling unsafe, and loneliness. Women are more likely to experience emotional issues such as depression, and anxiety related to olfactory impairment.

The pathophysiology of the Olfactory and Gustatory (Taste) loss in Upper Respiratory Tract Infection (URTI) is not yet completely clear and different studies are focusing on it for a better understanding. There are different treatments for OD. These can include pharmacological options such as corticosteroids and non-pharmacological treatments like Olfactory Training or surgical procedures in cases of nasal polyps or sinusitis causing smell loss. Corticosteroids have different adverse effects such as immunosuppressive action (which reduces immunity as an adverse effect), which often make them an unsuitable option, especially during a pandemic.

Olfactory Training

Olfactory training is a non-pharmacological treatment performed by patients themselves two times a day over 12 weeks when they are exposed to 4 intense odors. Individuals try to remember the odor of the jar they smell by deeply sniffing and concentrating on its scent. (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). These odors are used as they are familiar to most people with the research showing statistical results (Odor Identification, Odor Discrimination, and Odor Threshold P-values respectively: .004, .001, and .005)*. Individuals try to remember the odor of the jar they smell by deeply sniffing and concentrating on its scent.

Source: https://www.entsc.com/taste-smell-kit-from-entsc/

Results from Previous Studies

Different studies have shown statistically significant results around this intervention. In one of the studies, the result in the treatment group using the olfactory training intervention showed significant improvement after a three-month course of treatment. Certain studies investigated short and long-term olfactory training in post-viral infection olfactory loss patients. These studies confirmed the efficacy of olfactory training as a treatment for smell loss. Researchers found that increasing the duration of intervention use (up to 56 weeks) increases the success rate of olfactory treatment in patients.

These odors used in the olfactory training are subject to change according to cultural familiarity or even the age of individuals. For instance, children often use odors such as lollipops, chocolate, or popcorn as they are more familiar with them than the strong odors mentioned above (rose, eucalyptus, lemon, and clove).

Olfactory training can be practiced with any odors available to individuals. This practice has no considerable adverse effects, but it is still advisable for patients to begin olfactory training after consultation with a specialist or physician. “Improvement” of smelling sense helps in mitigating taste loss in post-COVID-19 patients and is briefly due to the anatomical structure of the neurons' correlation in the frontal lobe.


Speaking Plainly:

  • Different studies on olfactory training have shown significant improvement in smell Threshold, Discrimination, and Identification compared to pre and post-training.

  • A longer duration of olfactory training leads to the improvement of different aspects of one’s sense of smell.

  • Persistent Olfactory and Gustatory Dysfunction (smell and taste loss) require consultation with specialists for further check-ups and diagnosis.

*P-value below 0.05 is considered to be statistically significant.