Why Can't You Smell? Doctors and Scientists Are Working to Understand COVID-19's Impact on Our Senses

One of the telltale symptoms of coronavirus infection is a nightmare for wine lovers: loss of smell and taste. Researchers are studying why it happens and if it can be cured

Why Can't You Smell? Doctors and Scientists Are Working to Understand COVID-19's Impact on Our Senses
COVID-19 patients report losing their sense of smell and finding their wine tasteless. (Getty Images)
Jan 20, 2021

When Dr. Christian Squillante traveled to South Africa in February 2020, he enjoyed safari rides and explored the local wine regions. But halfway into the trip, the Minneapolis-based oncologist developed a fever and severe fatigue that lasted two days. He recovered quickly and didn't give it much thought until two weeks later, when he opened a bottle of Chenin Blanc he had brought back from his trip and found it tasted like water.

"I was having a friend over for one of our weekly wine nights and suddenly noticed that I couldn't taste anything," Squillante told Wine Spectator via email. "My loss of smell came on almost instantly." Nearly a year later, Squillante says his senses of taste and smell still haven't fully returned, and most flavors are "muted."

Pro golfer Greg Norman had a similar experience in December 2020, when he believes he contracted COVID-19 at a PGA Tour event in Orlando, Fla. Norman says he lost his sense of taste and smell about a week after the event.

"I was experiencing other symptoms first, like bad back pain, joint aches and fever, and I noticed the roof of my mouth was very 'pasty,'" Norman told Wine Spectator via email. "My senses have returned, but only in the past few days."

Squillante and Norman are among many whose lifelong love of wine has been endangered by the coronavirus thanks to olfactory dysfunction (OD). More than a year after the first cases emerged, scientists are still trying to figure out key questions. Why do we lose our sense of taste and smell? Why do some recover more quickly than others? And can the virus cause permanent loss?


Can you train your nose to smell wine again? Contributing Editor Robert Camuto has been trying just that, after being diagnosed with COVID-19 last month.


A neurologist's take

Dr. Felicia Chow is a neuroinfectious disease specialist at the University of California at San Francisco and has seen numerous patients suffering from lost sense of taste and smell. According to Chow, the nose contains multiple types of cells, including neurons that sense different odors and transmit signals to the brain, as well as supporting cells along the nasal epithelium.

"It seems like the virus in the nose itself is not infecting the actual smell neurons or the nerve cells that help us to smell, but rather the supporting cells," Chow told Wine Spectator. "Those supporting cells play an important role, and when those are infected it seems to impair our sense of smell."

It is unknown why the effects can last so long, but Chow says she was relieved when her team learned it wasn't the neurons that were being infected, since patients would have to wait for those cells to regenerate before a sense of smell could return. Supporting cells in the epithelium lining turn over rapidly. That seems to be the reason why many patients, such as Norman, have experienced a relatively quick return of their senses.

"One thing to think about is the severity in the number of supporting cells that have been wiped out by the virus," she said. "The more severe, the higher burden that correlates with the period of time for those supporting cells to regenerate and for you to get your sense of smell back, so maybe that explains some of the variability in time to recovery."

Unfortunately, treatments and training regimens aren't very successful in speeding the road to recovery, Chow has found. She says that with her patients neither steroids, acupuncture nor retraining senses to try and bring them back (olfactory training) seems to work. Time, she believes, is the key to recovery.

Although Chow hasn't found evidence that olfactory training works, others are trying it and recent studies suggest it might have benefits. A meta-analysis of 16 studies published in the National Library of Medicine found that patients with post-viral olfactory dysfunction who received smell training were nearly three times more likely to achieve a significant difference in olfactory testing scores.

The training involved twice-daily exposure to a set of four odors, including rose, eucalyptus, lemon and cloves, which patients smelled for 10 seconds or longer, rotating through each. The study also found that post-viral patients were shown to benefit the most from smell training compared with cohorts suffering from other causes of olfactory dysfunction.

Certain patients, such as Norman, claim that wine tastes differently during and shortly after experiencing the virus. Norman got a bitter acidic taste from a glass at home, while others say flavors that were once distinguishable are now altered.

"What we find is that sometimes as cells figure things out, there are signals that direct them to the right place," Chow said. "Over time it could correct itself."

As patients await a full return of their sense of taste and smell, Chow warns them to keep eating. Weight loss is a huge issue since much of our enjoyment in eating comes from taste and smell, so it's important to stay vigilant and get enough calories.

What's the research saying?

Since March 2020, scientists have been researching OD. A recent European study published in the Journal of Internal Medicine investigated how COVID-19 patients recovered their olfactory senses according to disease severity, and found that the prevalence of OD was higher in mild rather than severe cases.

Dr. J.R. Lechien and his team collected data from more than 2,500 patients with laboratory-confirmed diagnoses of COVID-19 in 18 different European hospitals from March 22 to June 3 of 2020. They separated patients into four groups: mild, moderate, severe and critical cases. Each group was defined by the COVID-19 Disease Severity Scoring of the World Health Organization (WHO), which defined a mild case as someone without viral pneumonia, a moderate as having clinical signs of pneumonia, a severe patient as having clinical signs of pneumonia plus respiratory distress and critical as having acute respiratory distress syndrome or septic shock and being hospitalized in the ICU.

The team used online questionnaires and olfactory evaluations for 233 patients in order to track OD at 30 days, 60 days and six months. The olfactory evaluations consisted of Sniffin-Sticks tests, a standardized psychophysical olfactory evaluation using 16 smell pens. Patients who scored low were invited to repeat the evaluation until scores returned to normal levels.

Of the 2,581 patients evaluated, 1,916 reported OD. Over 85 percent of those were mild patients, while less than 7 percent of those with impacted sense of smell were severe to critical patients. Of the 233 patients who underwent the olfactory evaluations, 181 had mild cases of COVID-19, and most recovered their sense of smell over the course of six months.

"Our study reports that the prevalence of olfactory dysfunction is higher in mild form and significantly decreased from mild to critical form," Lechien told Wine Spectator via email. He says that their hypothesis is that mild patients had a better immune response by localizing the infection and stopping it from spreading to the rest of the body. The downside is that these patients could have a stronger impairment of olfactory cells as a result.

The novelty of the new coronavirus and limited research means expertise is limited. Lechien says that he would try to increase the number of patients undergoing psychophysical testing and include additional collaborators for future studies in order to advance his results. He is planning to investigate OD and recovery among different age groups next.

A separate analysis published by the Mayo Foundation for Medical Education and Research concurred with some of the assumptions gathered from Lechien's findings. Researchers compiled results from 24 studies with more than 8,000 patients in 13 countries. It estimated the prevalence of OD among COVID-19 patients, and found that the older the patients the lower the prevalence of OD. (The study notes, however, that few of the studies that were analyzed used objective assessment methods for establishing the presence of OD. Most relied on self-reporting by patients.)

Recovery

Squillante feels that his sense of taste and smell is at 40 percent since contracting the virus. While he still enjoys physical sensations from sparkling wine, chilled rosé and even the textures of a heavy Cabernet, the flavor is subdued. But he says this experience has taught him some lessons.

Getting into wine at an early age, Squillante spent a decade of his younger years collecting over 200 special bottles he was hoping to enjoy, but now, he doubts it will happen. A piece of advice he gives to fellow wine lovers is to drink those special bottles in the cellar. "You don't always have to save it for the future," he says.

Losing his senses also helped Squillante realize that wine is more than just a drink. "While I may not enjoy it on a personal level like I once did, I still find the social aspects of wine to be very rewarding," he said. "I can still enjoy that special bottle by opening it and serving it to my friends and family."

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