Loss of smell and taste from Covid is reversible over time, study finds
“I grabbed a cup of coffee in the morning, and it just tasted hot,” said Clark, who is a national media strategist at the University of Florida.
“I had felt so good while I was quarantining I thought maybe this was a false positive but then when that happened I thought ‘OK, it’s real,'” Clark said.
A few months later, she was washing her hair with her favorite scented shampoo when she noticed an unusual odor.
“Lavender is my favorite smell, but now the shampoo smelled like sulfur and gunpowder,” she said.
Suddenly lots of things smelled odd, or distorted. Red meat smelled “hideous, rotten,” and anything with rubbing alcohol smelled “revolting.”
“The absolute worst is hand sanitizer, because it’s everywhere. It smells like cheap tequila and ham with notes of old lady perfume,” Clark said.
“Or what I think that might smell like,” she added. “It’s not a smell I’ve ever smelled in the real world, for sure.”
Clark is suffering from parosmia, a distortion of smell that occurs when receptor cells in the nose don’t detect and translate odors to the brain properly. It can happen after a bad cold or sinus infection, head injury, seizures and certain drugs.
Parosmia has also been associated with a complete loss of smell and taste, called anosmia, that has become a hallmark sign of mild to moderate Covid-19 infections.
Six months after her Covid-19 diagnosis, Clark’s nose is still in recovery.
“I can detect smells — I just can’t really tell what they are,” Clark said. “So I’m hoping this parosmia is the brain trying to fire back up and and start smelling again.”
A year to recover
The study followed 97 Covid-19 patients who had lost their sense of taste and smell for up to a year. Every four months, all patients were asked to tell researchers how they felt their olfactory function was recovering. Of the study participants, 51 also underwent objective testing to check their ability to smell at each four-month interval.
“At eight months, objective olfactory assessment confirmed full recovery in 49 of 51 patients (96.1%),” Dr. Marion Renaud, an otolaryngologist at University Hospitals of Strasbourg in France, and colleagues wrote in the study.
Of the two patients who had not fully recovered, one was able to smell, but abnormally, while the other had not recovered the ability to smell.
An intriguing additional finding was that many of the people who had recovered their olfactory function as rated by an objective sniff test continued to believe their sense of taste and smell was reduced. Of the 49 who tested as fully recovered, only 23 said they felt their sense of smell had fully returned.
“This highlights the importance of applying both methods for postviral olfactory disorder evaluation,” the researchers wrote.
An early sign of Covid-19
Can you check your smell at home?
Yes, there are several ways to accurately test your sense of smell at home, experts say. One is the jellybean test.
“You put the jellybean in your mouth, and chew it. Let’s say it’s a fruit flavor jellybean: if you get the savory plus the sweetness of the jellybean you’ll know you have functional taste,” Munger said.
“Then, while still chewing, suddenly release your nose. If you have a sense of smell you’ll suddenly get all the odors and you’ll say ‘Oh! that’s a lemon jellybean,’ or ‘Oh! that’s cherry.’ It’s really a very dramatic, quick, ‘Wow’ type of response,” he explained.
“If you can go from sweet and sour to the full flavor and know what the flavor is,” Munger said, “then your sense of smell is probably in pretty good shape.”
The scientific name for this process is retro nasal olfaction, where the odors flow from the back of your mouth up through your nasal pharynx and into your nasal cavity.
But what if you don’t have a jellybean? You can use other foods too, said ear, nose and throat specialist Dr. Erich Voigt, director of the division of sleep otolaryngology at NYU Langone Health.
“The pure smell sense would be if you can smell a particular substance that’s not stimulating other nerves,” Voigt said. “So some examples of that would be if you can smell ground coffee or coffee brewing, or if you can smell someone peeling an orange. That’s the smell sense.”
But you have to be careful, because it’s easy to think you’re using your sense of smell when you’re not, Voigt said.
“So for example, ammonia or cleaning solutions, those stimulate the trigeminal nerve, which is an irritant nerve,” he said. “And so people will think, ‘Oh, I can smell Clorox, I can smell ammonia, which means I can smell.’ But no, that’s not correct. They’re not actually smelling, they’re using the trigeminal nerve.”
Still aren’t sure if you’re getting it right? Check the internet for medically based scratch and sniff tests.
If you are experiencing a loss of smell, take care because there are dangers such as not being able to smell a gas leak, or perceive rotten milk or rancid food.
CNN’s Jacqueline Howard and Lauren Mascarenhas contributed to this report.