The loss of smell or taste is one of the most common symptoms of COVID-19. Those senses usually return to normal within weeks, but as coronavirus infections continue, doctors worry a significant number of patients are facing a long-term or even permanent problem.
Losing the sense of smell — which then impacts taste — can have a larger practical and psychological impact than people realize, affecting everything from appetite to how a person relates to the world.
A whole generation of people will be affected, said Dr. Rakesh Chandra, a researcher at the Smell and Taste Center at Vanderbilt University Medical Center in Nashville, Tennessee.
“I don't think COVID is going away. I think we’ll see outbreaks that look like multiple rolling hills, with each subsequent hill smaller than the one before it,” Chandra, who is also a professor of otolaryngology and chief of rhinology and skull base surgery at the hospital, told TODAY.
“With each of those, there's going to be some percent of people who are going to have total or near-total smell loss and since people generally don't die from COVID, the percent of the population who then is walking around with that problem is just going to get larger.”
When Chandra and his colleagues surveyed more than 1,000 adult COVID-19 patients, almost 11% reported partially or completely losing their smell for more than six weeks.
Other studies were even more worrisome. A survey of 798 adult COVID-19 patients who lost their sense of smell and taste, conducted by researchers at Virginia Commonwealth University School of Medicine in Richmond, found about 20% still did not recover their smell function by six months after infection.
That percentage is “a lot of people, given the millions that have been afflicted with COVID-19,” said Dr. Evan Reiter, medical director of the Smell and Taste Disorders Center at VCU Health and a co-investigator on the study, in a statement.
There have been more than 237 million confirmed cases of COVID-19 reported to the World Health Organization as of October. If either survey reflects what’s happening worldwide, tens of millions of people around the globe could be walking around with an impaired sense of smell months after being infected.
Chandra suspected that as more people are followed long-term, the number of COVID-19 patients who permanently lose their sense of smell will settle at 5% to 6% or so.
Most people wouldn’t think it’s a big deal, but the impact can be devastating. Eating — a big part of how we enjoy our day-to-day existence — is deprived of much of its sensory pleasure. Other smells, like the fragrance of flowers, perfume, rain or freshly-cut grass are gone, too. Even your home has a unique smell — would you still feel home without it? There’s also no alert system for smoke or food that’s gone bad.
“We take for granted what we're smelling. But we literally live in a medium of fluid air and with the sense of smell, we're constantly sampling our environment… interacting with it in a moment-by-moment way just by breathing, the subtleties of it,” Chandra said.
“It’s very detaching to not have that … there's a certain blackout feel.”
Smell also feeds into a part of the brain involved in emotional sense and memory, he added, so it’s an intricate part of our psychology.
In a recent survey of adults with COVID-19-associated “smell and taste disturbances,” 87% complained about reduced enjoyment of food and 43% reported depression.
It’s possible to lose appetite, which then leads to weight loss, though Chandra noted some patients can actually gain weight because they eat more salt and sugar to compensate for their altered senses. Taste buds on the tongue still allow people to recognize whether something tastes sweet, sour, bitter or salty, but smell is needed for flavor perception.
What can be done?
The new coronavirus doesn’t have a direct effect on smell nerve cells; instead, it appears to infect the supporting cells around them, Chandra said. Even in patients with long-term loss, it’s possible for the olfactory system to eventually rewire itself, allowing things to return to somewhat normal, he added.
People younger than 40 are more likely to recover COVID-19-related smell and taste loss than older adults, the researchers at Virginia Commonwealth University School of Medicine found.
As unpleasant as it is, patients who go from smelling nothing to having a distorted sense of smell — where everything smells rotten or different than before — probably have a better prognosis because it means they have some underlying neural function, Chandra noted.
To boost the chances of recovering the sense of smell, both he and Reiter recommended olfactory training using essential oils, which involves smelling scents such as rose, lemon, eucalyptus and clove for a few seconds twice a day for at least three months. It can help restore some of the ability to identify and discriminate between odors.
“Potentially, it may get people a little bit more tuned into whatever level of function they have left so it might make them more sensitive and better able to use the remaining sensors and neurons that are working,” Reiter said. “It’s low cost and low risk.”
Patients can also try anti-inflammatory steroids that have been formulated as nasal sprays — a treatment that’s usually meant for people with chronic sinusitis: “We have people flush their noses out with it. That might help; it might not. It doesn't hurt anything,” Chandra said.
Eating an anti-inflammatory diet high in omega-3 fatty acids is another option to try, he added.
If patients had COVID-19 three months ago and still can’t smell after trying all of those things, their senses probably will not return to what they were before the infection, Chandra noted.
These patients may one day benefit from technology similar to a cochlear implant — a device that uses a sensor to detect odor molecules in the air and tell the brain to sense the correct smell. Researchers at Virginia Commonwealth University have been working on such a solution.