Recovery of olfactory capacity following a COVID-19 infection Sourced from the article “Récupération des capacités olfactives : un entraînement particulier est possible chez les professionnels du vin !” (Revue Française d’OEnologie, 2020). Original language of the article: French.
The loss of the sense of smell related to COVID-19 is not irreversible. It appears to last between eight and nine days on average, but can go on for several weeks for some patients. In order to help with the optimal recovery of your sense of smell and avoid qualitative disorders that sometimes arise after a period of anosmia, it is possible to train using simple exercises. However, the exercise protocols must be suited to the way in which the virus acts on the olfactory system by tapping into the specific skills of wine professionals.
Up to 86 % of individuals suffering from COVID-19 describe a loss of their olfactory performance. This loss of smell is not irremediable. It appears to last between eight and nine days on average, but can go on for several weeks for some patients
It is possible to strengthen or help olfactory recovery through simple exercises. Although disorders do not last very long for some COVID-19 sufferers, olfactory training should ease the functional recovery of smell insofar as it improves sensitivity to odors, their recognition and their identification. It so happens that people who use their sense of smell professionally quite often unintentionally develop exceptional olfactory abilities. We can draw on their experience to our benefit. Among other things, the exercise protocols must be suited to the way the virus acts on the olfactory system, which appears to be indirectly affected in the case of COVID-19. In fact, tissue inflammation leads to the obstruction of the nasal cavities and thus hinders access to the receptor cells (olfactory neurons), affecting the subjects’ ability to detect and identify smells.
Which training methods can be used?
1 – Training through olfactory mental imaging
To begin with, given that the nasal cavities are obstructed, it would be ineffective to try smelling fragrant samples - these sessions will take place at a later stage. We do, however, believe that it would be healthy to continue exercising the process of air sampling that we call sniffing.
In the absence of actual, objective perception, the first useful exercise could be an olfactory mental imaging task. Its objective is to stimulate the ability to imagine smells in the absence of the odorant source. We then create a sort of olfactory hallucination on-demand, that does not involve smelling the oder, instead perceiving it. This competence is particularly well developed in olfactory experts, such as wine professionals
It is important to carry out this exercise daily and to focus for about ten days on the same odors (in the aforementioned study, the tasters were instructed to imagine two smells daily, for several minutes at a time). In the following days, it is possible to attempt to carry out the same task with two new smells.
Figure 1. Reduction in detection thresholds through learning. Here we compare the effect of training through repeated exposure (A) and through olfactory mental imaging (B) on sensitivity to 1-octen-3-one (an earthy-moldy defect in wines; giving off a mushroom-like odor). In both cases, a decrease in the detection threshold, therefore an increase in sensitivity, is observed. The gains obtained (8.9 and 9.4) through both methods are very similar (adaptation of Tempere et al., 2014)

The purpose of this exercise is to stimulate your olfactory system, which is no longer able to be activated by everyday smells, in order to maintain its abilities.
2 – Training through repeated exposure to odors
Later on, having regained olfactory sensitivity, a training exercise involving repeated exposure to various odorant sources can be set up. Daily exposure to odorants (perfumes, spices, essential oils, pastry flavorings, etc.) can alter the sensitivity, the ability to discern and identify the smells to be ‘relearned'. Training through repeated exposure can enable specific anosmic subjects to recover some degree of sensitivity. Furthermore, the repeated scenting of wines (as well as their tasting) can improve the ability to differentiate them
The physiological effects of such simple training through repeated exposure are directly highlighted in the olfactory epithelium, the olfactory bulb, which can lead to neuronal alterations that influence the brain pathway of olfactory information.
To make the most of this training, certain precautions should be taken (Tempere et al., 2012)
Repeatedly sniff each odorant for about thirty seconds. Repeat this exercise daily for several weeks (from 1 to 3 months). It is then possible to extend the training by repeating the exercise with other odorant sources.
Finally, these exercises can either be carried out blindly, or by mentioning the name of the odorant. Indeed, the descriptor-smell association facilitates recollection.
Note that these exercises can be carried out even under regular perceptive conditions, in the absence of generalized olfactory disorders. For example, they are effective in the recovery of specific anosmic afflictions
The translation of this article into English was offered to you by Moët Hennessy.
NOTES
- Lechien J.R., Chiesa‑Estomba C.M.et al. (2020). Olfactory and gustatory dysfunctions as a clinical presentation of mild‑to‑moderate forms of the coronavirus disease (COVID‑19): a multicenter European study. European Archives of Oto-Rhino-Laryngology, p. 1-11.
- Tempere S., Hamtat M., Bougeant J.C., de Revel G., Sicard G. (2014). Learning Odors: The Impact of Visual and Olfactory Mental Imagery Training on Odor Perception. Journal of Sensory Science, 29, 6, p. 435-449.
- Djordjevic J., Zatorre R., Petrides M., Boyle J.A., Jones-Gotman M. (2005). Functional neuroimaging of odor imagery. Neuroimage, 24, p. 791-801.
- Tempere S., Hamtat M., Bougeant J.C., de Revel G., Sicard G. (2014). Learning Odors: The Impact of Visual and Olfactory Mental Imagery Training on Odor Perception. Journal of Sensory Science, 29, 6, p. 435-449.
- Tempere S., Hamtat M., Bougeant J.C., de Revel G., Sicard G. (2014). Learning Odors: The Impact of Visual and Olfactory Mental Imagery Training on Odor Perception. Journal of Sensory Science, 29, 6, p. 435-449.
- Hughson A.L., Boakes R.A. (2009). Passive perceptual learning in relation to wine: Short-term recognition and verbal description. The Quatertly Journal of Experimental Psychology, 62, 1, p. 1-8.
- Li W., Luxenberg E., Parrich T., Gottfried J.A. (2006). Learning to smell the roses: Experience-dependent neural plasticity in human piriform and orbitofrontal cortices. Neuron, 52, 6, p. 1097-1108.
- Tempere S., Cuzange E., Bougeant J.C., de Revel G., Sicard G. (2012). Explicit sensory training improves the olfactory sensitivity of wine experts. Chemosensory Perception, 5, 2, p. 205-213.
- Patel Z.M., Wise S.K., DelGaudio J.M. (2017). Randomized controlled trial demonstrating cost-effective method of olfactory training in clinical practice: essential oils at uncontrolled concentration. Laryngoscope Investigative Otolaryngology, 2, 2, p. 53-56.
- Tempere S., Hamtat M., Bougeant J.C., de Revel G., Sicard G. (2014). Learning Odors: The Impact of Visual and Olfactory Mental Imagery Training on Odor Perception. Journal of Sensory Science, 29, 6, p. 435-449.
References
- Lechien J.R., Chiesa‑Estomba C.M. et al. (2020). Olfactory and gustatory dysfunctions as a clinical presentation of mild‑to‑moderate forms of the coronavirus disease (COVID‑19): a multicenter European study. European Archives of Oto-Rhino-Laryngology, p. 1-11.
- Tempere S., Hamtat M., Bougeant J.C., de Revel G., Sicard G. (2014). Learning Odors: The Impact of Visual and Olfactory Mental Imagery Training on Odor Perception. Journal of Sensory Science, 29, 6, p. 435-449.
- Djordjevic J., Zatorre R., Petrides M., Boyle J.A., Jones-Gotman M. (2005). Functional neuroimaging of odor imagery. Neuroimage, 24, p. 791-801.
- Hughson A.L., Boakes R.A. (2009). Passive perceptual learning in relation to wine: Short-term recognition and verbal description. The Quatertly Journal of Experimental Psychology, 62, 1, p. 1-8.
- Li W., Luxenberg E., Parrich T., Gottfried J.A. (2006). Learning to smell the roses: Experience-dependent neural plasticity in human piriform and orbitofrontal cortices. Neuron, 52, 6, p. 1097-1108.
- Patel Z.M., Wise S.K., DelGaudio J.M. (2017). Randomized controlled trial demonstrating cost-effective method of olfactory training in clinical practice: essential oils at uncontrolled concentration. Laryngoscope Investigative Otolaryngology, 2, 2, p. 53-56.
- Tempere S., Cuzange E., Bougeant J.C., de Revel G., Sicard G. (2012). Explicit sensory training improves the olfactory sensitivity of wine experts. Chemosensory Perception, 5, 2, p. 205-21
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