Losing Your Sense of Taste and Smell With the Coronavirus

One day in the spring of 2020, around the time much of the country went on lockdown to blunt the spread of the coronavirus, Sara Buursma felt run-down and was battling a low-grade fever. "I was working a lot, and I have three young kids," she says. "I thought it was a common cold."

Three days later, Buursma lost two of her major senses. "I couldn't smell anything," she says. "I tried smelling essential oils and peppermint oil, which usually makes my eyes water. I couldn't smell anything."

Buursma also was unable to taste food -- including her favorite flavor of Ben & Jerry's ice cream. "I was so disappointed," she says. "You want something good to eat when you're feeling terrible."

Three weeks later, Buursma experienced chest congestion and a severe, dry cough. Shortly after that, she was diagnosed with COVID-19. The diagnosis explained Buursma's sudden loss of taste and smell.

Anosmia is a condition that causes a person to "partially or completely lose his or her sense of smell," according to Yale Medicine. "Some people are born without the sense of smell, which is a condition called congenital anosmia." This is a common symptom of the coronavirus, which is not surprising, according to the American Academy of Otolaryngology--Head and Neck Surgery, which says that "viral infections are a leading cause of loss of sense of smell, and COVID-19 is caused by a virus." Symptoms of anosmia include not just the loss of smell but changes in how food tastes.

In fact, it's not unusual to lose sense of smell with any viral infection in the nose, including other coronaviruses that cause the common cold. The academy says that a group of otolaryngologists in the U.K. noted that 2 out of 3 confirmed COVID-19 cases in Germany reported a loss of sense of smell and 30% of people in South Korea with mild symptoms who tested positive for COVID-19 reported anosmia as their main symptom.

[See: What Are the Symptoms of Coronavirus?]

Smell Plus Taste Equals Flavor

Research suggests that as many as 70% of people who contract COVID-19 lose their sense of smell, says Dr. Marc Sala, a pulmonary and critical care specialist at the Northwestern Medicine Comprehensive COVID-19 Center in Chicago. Most of these patients regain their senses of smell and taste within about eight weeks.

Taste, however, is another issue. "The definition of taste to a patient and to a physician are very different," said Dr. Joseph K. Han, professor of otolaryngology, director of the division of rhinology and endoscopic sinus-skull base surgery and director of the division of allergy at Eastern Virginia Medical School.

"Physicians talk about the five taste sensations," he says.

The five taste sensations are:

-- Sweet.

-- Sour.

-- Salty.

-- Bitter.

-- Umami (often described as savory).

Viruses don't typically affect those senses directly. "Losing sense of taste is from a completely different nerve system, a different disease process," Han says.

While there's evidence indicating that COVID-19 affects the taste system of some people, the exact mechanism is not known, says Steven Munger, director of the University of Florida Center for Smell and Taste, located within UF's McKnight Brain Institute in Gainesville, Florida. This is independent of the impact of smell loss on flavor.

Yet, even if the sense of taste is not altered, smell has a direct effect on how we perceive the flavor of foods, Han says. "We should use the term sense of flavor, because flavor isn't taste, it is smell."

"Flavor is the perception created by your brain when it combines the smell and taste of food or drink," Munger adds. "Smell, not taste, is what allows you to distinguish lemon from lime; both taste sour, but they smell slightly different."

Some people with COVID-19 also lose chemesthesis, the ability to sense chemicals in chili peppers, herbs and spices such as capsaicin in a jalapeno or menthol in mint.

More than a year after she lost both her sense of smell and taste, Buursma says her sense of taste hasn't fully returned. "Things still don't taste right," she says. "There are times when I (eat something and) think, 'I don't like this like I used to.'"

[Read: If I Get Coronavirus, Can I Get It Again?]

Theories About the Coronavirus and Sense of Smell

How does this coronavirus disrupt the sense of smell? "There are three leading theories," Munger says.

-- The first is that the virus is using the olfactory nerve to transfer across the skull into the brain.

-- The second suggests the virus is attacking sensory cells themselves, "damaging or mucking up the works," he says.

-- The third possibility is that the virus is attacking nasal tissues more generally, causing inflammation or other disease processes that interfere with normal smelling function.

This last idea currently has the greatest scientific support. "An extensive analysis of gene expression data in nasal tissue has found that two genes important for the entry of this class of viruses into cells are found to be turned on in nasal cells that surround the nerve cells that sense odors, but not in those sensory nerve cells themselves," Munger says.

[See: Myths About Coronavirus.]

This suggests the virus causes a more global, perhaps inflammatory response that disrupts the ability to smell, Munger says. He adds that most patients are reporting they get their sense of smell back after a few weeks, "which would be consistent with the type of smell loss with any upper respiratory infection." However, research suggests that about 5% of these patients have prolonged, and perhaps permanent, smell loss. Distorted smell, or parosmia, is also being reported in some patients.

Scientists and clinicians around the world who study smell and taste are working together to fast-track data collection on this symptom of COVID-19 and to develop tests patients can do at home.

"It is now clear that smell loss is the most predictive symptom of COVID-19, more so than others like fever or cough," Munger says. "We and others are now studying whether smell testing -- particularly in the school, workplace or home -- could be used to provide an early warning of COVID-19. We also hope that the increased awareness of anosmia will result in more regular screening of smell function as part of regular health care."