(CNN) – According to a new study of more than 2,500 patients from 18 European hospitals, about 86% of people with mild cases of Covid-19 lose their sense of smell and taste, but recover within six months.
A case of Covid-19 was considered mild if there was no evidence of viral pneumonia or oxygen loss and the patient was able to recover at home.
The sense of smell reappeared after an average of 18 to 21 days, the study found, but about 5% of people had not yet recovered olfactory function after six months.
Anosmia, which is a loss of smell and therefore taste, has been suggested as an early sign of Covid-19. It can occur without any prior warning, even with a stuffy nose.
“Anosmia has been particularly observed in patients who eventually tested positive for the coronavirus with no other symptoms,” said the American Academy of Otolaryngology-Head and Neck Surgery.
Moderate to Severe Covid-19
In comparison, the study found that only 4% to 7% of people with moderate to severe symptoms of Covid-19 lost their ability to smell and taste.
People with moderate Covid-19 had “clinical symptoms of pneumonia,” the study said, such as coughing, fever, and difficulty breathing. Those with critical cases of the disease suffered from severe respiratory problems, were more often older, and had “hypertension, diabetes, stomach disorders, kidney, respiratory, heart, liver, and neurological disorders.”
The study, 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 further analysis, the researchers said.
How to test your sense of smell
Is there anything you can do at home to test if you are experiencing odor loss? The answer is yes, using the “jellybean test”.
“You take a jelly bean in one hand and with the other you hold your nose tightly so you don’t get any airflow,” Steven Munger, director of the Center for Smell and Taste at the University of Florida, told CNN in a preliminary interview.
You put the jelly bean in your mouth and chew it. Let’s say it’s a fruit-flavored jelly bean: When you get the savory plus the sweetness of the jelly bean, you know you have a functional taste, ”said Munger.
Then, while you are still chewing, suddenly let go of your nose. When you have the sense of smell, you suddenly get all the smells and say ‘Oh! that’s a lemon jelly, ‘or’ Oh! that’s cherry. “It’s really a very dramatic, quick ‘Wow’ type response,” he explained.
“So if you can go from sweet and sour to full flavor and know what the flavor is,” said Munger, “then your sense of smell is probably in pretty good shape.”
The scientific name for this process is retro nasal smell, in which the scents flow from the back of your mouth up through your nasal cavity and into your nasal cavity.
But what if you don’t have a jelly bean? You can also consume other foods, said ear, nose and throat specialist Dr. Erich Voigt, director of the sleep otolaryngology department at NYU Langone Health, in a previous interview.
“The pure sense of smell would be if you could smell a particular substance that doesn’t stimulate other stomach nerves,” Voigt said. “If you can smell the smell of ground coffee or the brewing coffee, or if you can smell someone peeling an orange, that’s the smell.”
You have to be careful, though, 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, that stimulate the trigeminal nerve, which is an irritating nerve,” he said. And so people will think, ‘Oh, I smell Clorox, I smell ammonia, which means I can smell. But no, that’s not right. They don’t really smell, they use the trigeminal nerve. “
Still not sure if you are doing it right? Check the internet for medically based scratch and sniff tests.
Odor loss is common
Of course, not everyone who does a scent test gets the corona virus. Any respiratory virus, such as a cold or flu, temporarily affects smell and taste, sometimes even permanently.
“The amount of swelling that can occur in the nose as a result of the viral effect can prevent the odor particles from getting all the way to the top of the nose where the olfactory nerve is located,” Voigt said. “When that swelling subsides, the sense of smell can return.”
But there are also neurotoxic viruses, some of which fall into the common cold category, Voigt said.
“If they are neurotoxic, it means that they damage the olfactory nerve and it essentially stops functioning,” he added. “Many of those cases can recover the odor over time, but sometimes it’s a permanent loss.”
A partial or complete chronic loss of smell is incredibly common, Munger said, affecting millions of Americans long before the new coronavirus hit the scene.
“About 13% of the population has a significant odor or taste disturbance,” he said.
In addition to the common cold and flu, other causes of loss of smell include nasal polyps, tumors, neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease, and traumatic brain or head trauma, including whiplash.
“If someone has been in a car accident or had a whiplash or head injury, it can also affect the tiny nerves that go from the brain to the nose,” Voigt said. “So a whiplash injury can also cause a permanent loss of sense of smell.”
Loss of taste is often associated with loss of smell because we depend on smell to identify flavors. But there can also be medical reasons: Some medicines can influence the taste; chemotherapy and radiation therapy can certainly disturb the taste; and then there is physical damage, such as nerves being cut during dental procedures.
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