At this stage in the coronavirus outbreak, it's been well-documented that COVID-19 patients often experience a loss of taste and smell, usually as one of the first symptoms. For most people, these senses return to normal within several weeks. But others have noticed substantial changes to previously familiar odors and flavors, if their taste and smell come back at all.
While losing taste and smell happens often with viral infections and even other coronaviruses, the way that COVID-19 affects a patient's nose and mouth seems different, according to Dr. Sandeep Robert Datta, a Harvard neuroscientist who co-authored a recent study on anosmia, aka loss of smell, published in Science Advances.
"In many cases, the reason you lose your sense of smell when you get a cold is that your mucus composition changes, your nose gets super stuffy," he told TODAY. "When your cold resolves, that inflammation goes away and you can smell again. In COVID, it doesn't appear that that's the main thing going on."
What do we know about COVID-19 and loss of taste and smell?
Research published in early July looked at 55 coronavirus patients who experienced impairment of taste or smell. Of these, most said their senses were either fully recovered or improved four weeks later, but about 11% reported that the symptoms had either not improved or gotten worse during that time.
According to Datta, "most people" who experience loss of taste or smell due to COVID-19 regain these senses "pretty quickly." He estimated within two to six weeks. That said, there's "a very real subset of patients" whose "anosmia lasts much, much longer," he added. "There are people who were infected at the beginning of the pandemic, and they still haven’t regained their sense of smell."
Of these patients, Datta said, many report changes to their sense of smell when it does return, a condition called parosmia. For example, your favorite shampoo might smell completely different, and "it can be extremely disconcerting," he said.
Datta's research, released in late July, found that one potential reason this could happen is that the virus may infect what he called "support cells" in the nose. These are not the cells that actually detect odors; rather, they're the cells that help those sensory neurons function properly.
"We think that in the people who have longer lasting anosmia, maybe the long-term lack of support from these (support) cells actually causes the sensory neurons to die," he explained. "The sensory neurons have to be regenerated ... and one possibility is that in people with COVID, that might actually take extra long."
As a result, the parosmia may arise when those sensory neurons are "reborn" and have to reintegrate into the body's olfactory system all over again, Datta said. He added that for taste, it seems like both support cells and actual taste cells "might be infectible" by the coronavirus, and the underlying mechanism behind taste alterations has "similarities" to smell.
Right now, it's not known why some patients' senses return normally and others' don't.
Will sense of smell and taste ever return normally for these patients?
For most people, loss of smell and taste is temporary, but there are people where it's unclear at this stage whether their senses will go back to normal. According to Datta, parosmia could resolve over time as the regrown sensory neurons go through a process of "refinement."
"From what limited clinical data there is ... I think there is hope for these patients," he said. "Our hope is that our research might one day lead to actual treatment ... Smell is an understudied sense, although it's profoundly important."
Dr. Alfred Iloreta, an otolaryngologist at Mount Sinai's Center for Post-COVID Care in New York City, told TODAY that research from previous viruses that cause anosmia shows "there's a small proportion (of patients) that the smell never returns."
He added that he tells his patients, to set their expectations, "there's a possibility that (taste and smell) won't ever come back."
What's it like to experience changes to your taste and smell?
Iloreta, who's seen a range of patients with anosmia and parosmia, as well as taste conditions, said there's "a wide spectrum of presentations." Some patients notice decreases in their perception of flavors and odors, whereas others notices changes in these senses.
A common symptom, he noted, is a "constant fire or burning, smoke smell," and others include a "foul, bitter smell" and "a feces-like smell." These patients often report significant changes to taste, too, as these two senses are closely linked. The combination can greatly diminish appetite, he added.
Marcus Tomoff, a 28-year-old from Tampa, Florida, who tested positive for COVID-19 in early June, told TODAY he noticed one morning, before any other symptoms, that he couldn't smell or taste bacon. Shortly after, he realized that all other tastes had been replaced by "a metal taste," and his lack of smell made him think he was congested.
Now, he said he only has "mild taste and smell." He can get whiffs of peppermint and lemons, but mostly he smells "burning" and tastes metal. Overall, the experience has "mentally drained" him, he said, adding, "It’s kind of been like life’s little pleasures taken away from me ... You’re pretty much just eating and drinking to survive."
Emi Boscamp, 28, a food editor at TODAY in New York City who was sick with COVID-19 in mid-March, said that one of her favorite herbs, cilantro, now smells "disgustingly soapy." She added that garlic and onions smell "putrid but taste fine." While her senses slowly returned over about six weeks, she dealt with anxiety as a result. "I’ll have to have a new job. I can’t be speaking about food if I can’t even taste it," she thought, at the time.
Jamie Glass, 47, of Monclair, New Jersey, told TODAY that she was sick in mid-March but still occasionally notices a "burnt plastic smell" and a "plastic-y taste" in her mouth. She's taken to adding extra seasoning to her cooking to compensate.
"It’s a little numbing, to be honest," she said. "You don’t realize how much ... being able to smell something can make you feel hungry."
Both Datta and Iloreta noted that existing research links loss of smell to depression and anxiety.
What can you do if you're experiencing long-term loss of taste and smell?
Datta said that smell training, "where you take a set of familiar odors and you repeatedly expose yourself to those odors," may improve a patient's "ability to associate an odor with a perception."
Iloreta has started a trial where patients take a high-purity fish oil supplement to see if it can improve sense of smell. Fish oil has anti-inflammatory properties and promotes growth of neurons, he said. If you're interested in trying this strategy yourself, talk to your doctor first. Other possible strategies that haven't been studied but are safe, he said, include topical nasal steroids, like Flonase.
Datta also recommended seeking help from support groups for people who have lost their sense of smell or taste like Abscent or the U.K.-based Fifth Sense, and participating in studies, like the Global Consortium for Chemosensory Research.
Iloreta stressed the importance of seeing a doctor if you're experiencing changes to taste or smell, not only because it can be an early sign of COVID-19, but it can also be an indicator of other conditions like Parkinson's or sinus disease.