'Life-altering:' As millions cope with smell loss from COVID-19, researchers find new explanations and possible treatments

Elizabeth Byland has trouble stomaching chicken these days, because it smells to her like poop. Cauliflower tastes like metal and carrots like soap.

"I've got a dog that smells like orange slices," she said.

It's an improvement from last summer when the Richmond, Virginia, resident caught COVID-19 and couldn't smell or taste anything from July until after Thanksgiving.

"It's really life-altering," said Byland, 34. "It feels like I've lost a piece of my identity."

As the pandemic continues, more information is accumulating about the loss of smell that afflicts as many as 70% to 80% of people who catch COVID-19 and seems particularly common among those with mild disease.

For most, the condition lasts only a few days or a few weeks. But for as many as one-third, the loss can last for months, said Dr. Evan Reiter, an ear, nose and throat specialist at Virginia Commonwealth University Health System in Richmond. It may even be permanent.

Now, a new understanding is emerging about what causes smell loss with COVID-19 and, eventually, how it might be treated.

Smell loss has long been reported as a result of infections, smoking or head trauma, and some people are born without the ability to smell. About 3% of Americans have little to no sense of smell, and 12% have smell dysfunctions, according to a 2016 study.

"You don't think it's as important 'til you don't have it," Reiter said.

Losing smell can make people feel disoriented and detached, said Pamela Dalton, a smell researcher at the Monell Chemical Senses Center in Philadelphia. "When they walk into a familiar environment there's a whole dimension that's missing. There's a blankness there," she said. "It affects how they eat, it affects how they interact with other people, and it certainly affects their emotional state."

For Byland and as many as 40% to 45% of those who lose their smell, when scents return, they seem to be out of whack, Reiter said. This may be more common with COVID-19 than other viruses, but it's not clear why, he said.

Such strange scents used to be considered miswirings: As smell returned after an injury or an illness, sometimes the connections got crossed and things that used to smell like one thing started smelling like another, Dalton said.

A few experts now think, however, that as smell returns, the full bouquet may not come back at once, she said. So people like Byland perceive only part of the usual scent – the chemicals that are common to chicken and poop, for instance – rather than the full range that normally indicates chicken.

Psychological toll of smell loss

The loss of smell can be dangerous. People who can't smell might miss gas fumes or fire.

But mostly the toll is psychological.

Since April 2020, Reiter has been regularly surveying people who recovered from COVID-19, asking about their sense of smell. More than 40% of those who lost their smell said they were left feeling depressed.

Depression may be connected to smell loss, Dalton said, not just because people are grieving their loss, but because there is a close connection between the brain's smell center and the spot where emotions are controlled. Without signals from the nose, it may dysregulate the emotional system.

Psychiatric disorders are often accompanied by changes in smell, and smell loss can signal impending dementia or Parkinson's years before the telltale signatures show up on brain scans.

While it's easy to identify when someone struggles to see or hear, a loss of smell and taste is invisible, which can be an added burden.

People are less conscious of their sense of smell than of vision or hearing, but they still use it constantly as they go through the world: recoiling from trash, reveling in the scent of a spring breeze.

Byland, a professor of improvisation at Virginia Commonwealth University and a former dancer and gymnast, walks 5 miles every morning – without the bouquet of fresh-cut grass or her neighbors' roses.

She misses the smell of her husband when she hugs him, and her mom's distinctive scent. She can't tell anymore what her own body smells like. "I can't smell my skin, my hair. It's strange," Byland said.

It can even be hard to talk about, she said, because there are so few words in our vocabulary to describe smells. "It's like there's always this void."

For Byland and many others, the loss of smell also has meant the loss of ability to enjoy food. Some people truly lose their ability to taste after an infection, Dalton said, while others lose the aromas from food when their smell goes.

Much of what people perceive as taste is actually the odor of, say, chocolate, as it melts on the tongue. Some people experience a global loss of taste, and some people find that sweet taste is more affected, Dalton said.

Although the pandemic has been isolating for everyone, not being able to smell or taste the turkey at Thanksgiving and similar missed moments amplified her sense of loss, Byland said.

"When someone loses two of their five sense due to COVID, the isolation can feel even greater," she said. "It always feels like you're just missing the mark."

Research opportunity for smell loss

The COVID-19 pandemic has put smell in the spotlight. In the history of modern scientific research, there has never been an event that caused such widespread smell loss.

"When millions of people lose their sense of smell suddenly, it really brings it home to them just how important this sensory system is to them on a daily basis," Dalton said. "We're able to study the recovery process in much greater depth and in a far greater cohort than ever before."

There are only about 600 researchers worldwide who study smell, Dalton said, compared with about 11,000 who study vision.

Perhaps because there are so many patients, the people who have lost their smell from COVID-19 seem to be more vocal and active than those left scentless by previous viral outbreaks, Reiter said. They want answers. Even after other long-term symptoms go away, he said, "they may still be dealing with this for the rest of their lives."

Close to 40% of people Reiter surveyed had loss of smell as either their first or only COVID-19 symptom, and about 10% report it as their only symptom.

Unexpectedly, Reiter said, people who are younger and less symptomatic with COVID-19 may be more likely to lose their smell after infection. It's not clear why, he said.

Perhaps older people who are more likely to have severe disease already have a reduced sense of smell and won't notice it as much. (The loss of smell increases with age: More than 22% of Black Americans over 65 suffer a loss of smell and 10% of white Americans, according to a 2017 study.)

Or someone who is hospitalized for three weeks might lose and regain their sense of smell without even noticing, he said.

Loss of smell is far more indicative of COVID-19 than fever, said Dalton, who helped create a program to screen for smell loss among workers, like nursing home employees.

They receive preprinted cards each of which has three boxes covered in plastic. Every morning, the worker pulls up the plastic and answers a few simple questions on their smartphone, tablet or computer: Which of these has an odor, how strong is it on a scale of 1 to 10, and which of four options does it most smell like?

Some people don't lose their sense of smell entirely with COVID-19, but if a strong scent is perceived as an 8 one day and a 2 or 3 the next, the person is probably infected, she said. "If you had a sudden loss of smell and you didn't just suffer a head injury, you are pretty much guaranteed to have COVID."

Dalton hopes the attention smell is receiving now will lead to a greater use of smell testing as part of regular medical exams and screening measures.

Causes of smell loss and steps toward treatment

The virus that causes COVID-19 is present in the lining of the nasal passages as well as the sensory neurons, the nervous system cells that enable the brain to interpret scents, French researchers Hervé Bourhy, Pierre-Marie Lledo, Marc Lecuit and colleagues found in a study published earlier this month.

The presence of the virus in this olfactory system explains why many people lose their smell when they are infected, Lledo said.

"That is the entry point for many viruses, so this was not unexpected," Bourhy added in the same interview, "but this was never demonstrated before in SARS-CoV-2."

If a person's immune system can fight off the virus while it remains in their olfactory system, it may never make it to their lungs, where it would likely make them sicker, Lledo said, perhaps explaining why loss of smell seems more common in people with mild infections.

Sensory neurons can replace themselves, while most other neurons last a lifetime.

Lledo said their study clearly shows that the virus can kill these sensory neurons. The need to grow new ones explains why it can take a while for people to recover their sense of smell after an infection, he said.

Smell usually should return within one to two months, and if it doesn't, he advises people to go see a doctor.

The direct path from the olfactory system into the brain may explain why some people complain of long-term brain fog or mood changes after COVID-19 infections, Bourhy said.

The team's findings suggest two ways to treat patients, Bourhy said: first by controlling the replication of the virus in the olfactory system and second by controlling inflammation that can linger after the virus has cleared.

For someone with long-lasting smell loss, a physician may want to test whether the patient still has the virus or to consider anti-inflammatory medications, Lledo said.

Getting vaccinated against COVID-19 might also help the body clear the virus, if it hasn't already, Lledo said. And the shots should also protect people from losing their sense of smell even if they get infected, Bourhy said.

Truly understanding what causes smell loss from COVID-19 and other causes will make a big difference for a field that hasn't always had a lot of answers, said Steven Munger, a smell expert and director of the Center for Smell and Taste at the University of Florida in Gainesville.

There are no proven treatments for restoring smell, though researchers are working in several cutting-edge areas, including gene therapy and implants.

Restoring smell is tricky, Munger and others said, because each scent is composed of thousands of chemicals in different concentrations, each activating different patterns of brain cells.

"If we understand what's going wrong, that gives us mechanisms and targets that we can hopefully work to fix," he said. "Otherwise, we're sort of going blind."

Smell training

It's not entirely clear whether smell training can restore smell. "The jury is still very much out," Munger said, but "there's no harm in trying it."

Smell training is simple and inexpensive: Take quick "bunny sniffs" of a few scents for five minutes every morning and every night.

The only downside, Dalton said, "is probably a little frustration." It can be boring to do these exercises, and it may be a few months before someone notices an improvement.

But studies have shown that smell training can help recover smell faster after it's lost and may promote recovery in someone who would never otherwise have regained their smell, she said.

"Smell is like a muscle. The more you use it, the better you can identify things in your environment," Dalton said.

How well the sense of smell continues with age depends on things like inflammation and mucus in the nose, but also how much people relied on their sense of smell. "I know plenty of people in their 70s and 80s who can detect minute quantities of things and identify them," Dalton said. "They tend to be people who sought out opportunities for smell whether it's cooking or gardening or whatever."

Training seems to work better when begun soon after a smell loss. "A year or two out from the loss of sense of smell, they probably are not going to get any benefit from that," Reiter said.

Duncan Boat, who runs a British charity for people who've lost their sense of smell and taste called Fifth Sense, said there's no need to buy fancy kits. Jars of spices will do just as well.

Pick smells that are familiar, advises Molly Birnbaum, editor-in-chief of "America's Test Kitchen Kids," who began studying smell when she lost her own sense 16 years ago after being struck by a car. Birnbaum, who had planned to be a chef, was forced to change her career goals.

Smell training helped her recover her sense of smell, Birnbaum said. "Who knows if it's exactly the way it was before I lost it?" she said, but at least she's no longer afraid to cook for other people.

Byland has been dutifully sniffing essential oils – lemon and eucalyptus– every morning and every night for months.

Now, she can override some of the awful smell of chicken by adding lots of spices, she said.

Talking about it helps, too, though she's still a little embarrassed to be complaining about smell at a time when so many have lost so much more. Byland didn't tell anyone but her mother, her husband and two close friends for months. Now, she said, she's ready to talk publicly about what she's going through.

"It helps to bring light back in to a very dark space that I think we have been in for a long time," she said.

She has been told it could take up to 18 months after her infection for her smell to fully return. Byland said she got her vaccine as soon as she was allowed, because she's terrified of catching COVID-19 a second time and losing even more.

As an improv instructor, Byland considers it part of her job to find the positive in the negative, so she has been looking for that out of this experience, too.

"I've never had to practice what I preach more, and also not letting this become my only narrative in life," she said.

She believes her daily sniffing explains why CeCe, her white Lhasa Apso, now smells like orange slices instead of something less pleasant. "I feel like that's a positive," she said, "and I'm leaning into it."

Contact Karen Weintraub at kweintraub@usatoday.com.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID-19 smell loss: new research explores causes, treatments