A case of Covid-19 was considered mild if there was no evidence of viral pneumonia or loss of oxygen and the patient could recover at home.
The study found that smell reappeared after an average of 18 to 21 days, but about 5% of people had not regained olfactory function at six months.
Covid-19 moderate to severe
Comparatively, the study found that only between 4% and 7% of people with moderate to severe symptoms of Covid-19 lost their olfactory and gustatory capacity.
People with moderate Covid-19 showed “clinical signs of pneumonia,” according to the study, such as cough, fever, and difficulty breathing. People with critical cases of the disease suffered from severe breathing difficulties and were more likely to be of legal age and have “hypertension, diabetes, gastric disorders, kidney disorders, respiratory, cardiac, hepatic and neurological disorders”.
The study, which was published Monday in the Journal of Internal Medicine, found a higher rate of olfactory dysfunction in younger patients compared to the elderly, but that association needs more detailed analysis, the researchers said.
How to test your sense of smell
Is there anything you can do at home to test if you smell? The answer is yes, by using the “jelly test.”
“You put the jelly in your mouth and chew it. Suppose it’s a fruit-flavored jelly: if you get the tasty plus the sweetness of the jelly, you’ll know you have a functional taste,” Munger said.
“Then, while you’re still chewing, let go of your nose all of a sudden. If you smell, you’ll suddenly get all the smells and say, ‘Oh, this is lemon jelly’ or ‘Oh, this is cherry.’ kind of very dramatic, quick response and ‘Wow’, ”he explained.
“So if you can go from sweet and bittersweet to full flavor and know what the flavor is,” Munger said, “your sense of smell is probably in good shape.”
The scientific name for this process is retro nasal olfactory, where odors flow from the mouth up through the nasal pharynx and into the nasal cavity.
But what if you don’t have jelly? You can also use other foods, according to the ear, nose and throat specialist, Dr. Erich Voigt, director of the sleep otolaryngology division of NYU Langone Health, in a previous interview.
“The pure sense of smell would be if you can smell a particular substance that doesn’t stimulate the other body’s nerves,” Voigt said. “If you can smell ground coffee or brewing coffee or if you smell someone peeling an orange, that’s the sense of smell.”
But you have to be careful, because it’s easy to think you use smell when you’re not, Voigt said.
“So, for example, ammonia or cleansing solutions, these stimulate the trigeminal nerve, which is an irritating 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 right. They don’t actually smell, they use the trigeminal nerve.”
Still not sure if you’re doing well? Check the internet for medical evidence of scratching and settling.
Loss of odors is common
Of course, not everyone who takes an odor test will have coronavirus. Any respiratory virus, such as a cold or flu, will temporarily affect your sense of smell and taste, sometimes even permanently.
“The amount of inflammation that can occur in the nose due to the viral effect can prevent odor particles from reaching the top of the nose where the olfactory nerve is located,” Voigt said. “When this swelling subsides, the sense of smell can return.”
But there are also neurotoxic viruses, some of which are in the common cold category, Voigt said.
“If they’re neurotoxic, that means they damage the olfactory nerve and it becomes essentially non-functional,” he added. “Many of these cases can regain odor over time, but sometimes it’s a permanent loss.”
Partial or complete chronic loss of smell is incredibly common, said Munger, which affects millions of Americans long before the new coronavirus explodes on the scene.
“About 13% of the population has a significant impairment in smell or taste,” he said.
In addition to colds and flu, other causes of olfactory loss include nasal polyps, tumors, neurodegenerative diseases such as Alzheimer’s or Parkinson’s, and traumatic brain injury or head trauma, including whiplash.
“If someone has had a car accident or suffered a brain or cervical injury, this could also affect the small nerves as they go from the brain to the nose,” Voigt said. “Therefore, a neck whiplash injury can also lead to permanent loss of smell.”
Loss of taste is usually associated with loss of smell, because we rely on smell to identify flavors. But there can also be medical reasons: some medications can affect taste; chemotherapy and radiation therapy can certainly alter the taste; and then there is physical damage, such as nerves cut during dental surgeries.