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Loss of Smell: an early signal of Covid-19 disease.
Could it be reversed by "Smell training"?



The loss of smell, or anosmia, is a condition we, wine tasters, fear as it can prevent us from enjoying wine.


That's why when a friend of mine told me she was afraid of losing her sense of smell due to COVID-19, I started paying more attention to the news reports and the progress in understanding this new disease.

Here is my understanding of the phenomenon and some hope for better recovery.


Experiencing a loss of smell due to COVID-19 infection


After a few months in the pandemic, the European media has started reporting loss of smell as a possible symptom.

Several writers shared their personal experiences on social platforms or published articles. Most of them reported that the loss of smell was not total, but things started to smell differently.  


Jack Holmes described the sensation as a "chemical burn" or "the overwhelming sense was the back of my nose had become the California foothills during fire season." [1]

Jamie Goode, wine blogger, and author shared that "wine started tasting very strange." [2] "It was as if some sensations were missing, while others were either made up by my brain or in some strange way I was becoming hypersensitive to particular aromas that ended up masking the others."


 Seth Stephens-Davidowitz, economist and data scientist, examined the links between Google searches and 10 COVID-19 symptoms. The top three searches were loss of smell, fever, and chills [3]. 

You may have seen the graph in the media; it shows the relationship between the Google searches for loss of smell and the number of COVID-19 cases in US states at the time.


A similar observation was made in Italy where this search topic also peaked while the epidemic was spreading there. It is not to say that we should rely on Google searches to identify potential symptoms of a new disease; several evidences must be cross-checked before that. That's maybe while it took some time for medical experts to acknowledge loss of smell as a COVID-19 symptom.


Scientists are rushing to understand this unusual loss of smell


It seemed strange that the anosmia reported by the COVID-19 patients was not accompanied by other typical symptoms, ie, an abundance of mucus blocking the olfactory passages and triggering the loss of smell. 


Researchers from Switzerland and Italy reported in early April that they found a possible explanation for the phenomena [4]. 

The supporting cells protecting the olfactory cells in the nasal cavity are directly in contact with the external world (see graph below). The scientists found evidence that these cells might be the receptors of the virus in the nose. The olfactory cells and neurons may be damaged, leading to the loss of smell, or the strange sensations reported by humans. 


Olfactory system

A large study is underway by the Global Consortium of Chemosensory Researchers (GCCR) formed in March 2020 by a group of international smells and taste researchers from 30+ countries. They have launched a patient survey to gather data and more evidence of the potential link of COVID-19 and loss of smell. Please share with anyone who could contribute. 



Eleven days after launching the survey, the scientists had collected 30,000 responses from COVID patients [6]. They found that, on average,

  • 80 % of patients lost normal ability to smell,
  • 69 % their ability to taste, and
  • 39% their ability to feel sensations in the mouth (e.g., heat/cold or pain).
  • 30-98% of hospitalized COVID patients also reported anosmia, the loss of smell.


Some positive news: loss of smell is likely temporary


I am no stranger to losing my smelling abilities during allergy season; It's annoying, but I know it's temporary. I have adopted a rigorous routine, including daily rinse with salt water and the use of a nasal corticoid spray. This helps me keep the temporary loss of smell at bay.

But what about this unknown disease?


Recover faster with smell training


Dr. Claire Hopkins, a professor of rhinology at King's College London and president of the British Rhinological Society, was the first expert in raising public awareness about loss of smell as a symptom of Coronavirus infection. She is also the one bringing some hope to patients on their smell recovery.

While there may not be a medical treatment to recover smells, Hopkins suggests "smell training."



Fortunately, as wine tasters, we train our nose to be able to assess wine and distinguish wine aromas. Smell training can be as simple as smelling spices in your kitchen cupboard, the soap or shampoo in your bathroom.

"Just repeating it, over and over, and what it may be doing is helping the brain focus on that amount of smell function that is still intact and allowing you to maximize it." Professor Steven Munger, Director of the University of Florida's Center for Smell and Taste, gave this advice in a recent interview. [5]


A two-step training program for wine professionals


A team of French researchers shared in July 2020 a training protocol for smell training or re-training [7].

They had collected evidence in 2012 and 1014 that their program increased the sensitivity of people with specific hyposmia (low sensitivity to a particular odorant) or anosmia (inability to detect a particular odorant).

They shared this program in a wine journal to help wine professionals recover from the loss of smell due to COVID 19 infection.


It is a two-step training that I detail for you in this short document.



It consists of a first phase in which you retrain the olfactory system by visualizing familiar smells and a second phase where you smell actual odorants, daily.

According to this report, “the physiological effects of such simple training through repeated exposures are directly highlighted in the olfactory epithelium, the olfactory bulb.”


Therefore, we should be hopeful should we lose our sense of smell due to a viral infection.


Since I became aware of the possible loss of smell due to Coronavirus, I pay particular attention and practice some smelling exercises here and there: while walking and enjoying the fragrance of spring flowers, or the smell of the earth after a storm.

You are welcome to join me!


Stay safe, and everything will be alright.



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Published April, 15 2020
Updated August 2, 2020


References:

[1] Loss of Smell Isn't Just a Coronavirus Symptom. It Could Be Key to Slowing the Spread. Jack Holmes, April 3, 2020

[2] AN ALTERED SENSE OF SMELL: EVERY WINE PROFESSIONAL'S BIGGEST FEAR. Jamie Goode, April 5, 2020

[3] Google Searches Can Help Us Find Emerging Covid-19 OutbreaksSeth Stephens-Davidowitz April 5, 2020

[4] SARS-CoV-2 receptor and entry genes are expressed by sustentacular cells in the human olfactory neuroepithelium  By Leon Fodoulian, Joel Tuberosa, Daniel Rossier, Basile N. Landis, Alan Carleton, Ivan Rodriguez. April 2, 2020

[5] Many people lost their sense of smell weeks ago. They're still waiting for it to come back . Sarah Dean, CNN, April 12 2020

[6] Why COVID-19 Makes People Lose Their Sense of Smell. Leslie Kay, June 13, 2020, Scientific American.

[7] Recovery of olfactory capacity following a COVID-19 infection.  Sophie Tempere, Gilles Sicard, Gilles de Revel. Published : 24 July 2020


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