One COVID-19 symptom that’s frequently Googled is "smell loss."
“There are actually a variety of reasons other than COVID-19 why someone may lose their sense of smell,” says Bobby Tajudeen, MD, director of rhinology, sinus surgery and skull base surgery at Rush University Medical Center. “It can be due to nasal or sinus inflammation, or other viral infections distinct from COVID-19. And it can even occur as a result of some neurodegenerative diseases, like Alzheimer’s or dementia , or vitamin deficiencies. Rarely tumors can present with smell loss.”
So how do you know if it’s COVID-19 or something else that’s keeping you from enjoying the fragrant scent of your Christmas tree or the aroma of freshly baked holiday treats? And when should you see a specialist for smell loss?
Tajudeen says that while smell loss from congestion or common viral infections and COVID-19-related smell loss may feel the same on the surface, what’s happening internally and how the symptoms present themselves is actually very different.
Why am I losing my sense of smell?
According to Tajudeen, smell loss is most commonly caused by nasal and sinus inflammation. This inflammation can occur due to sinusitis, polyps in the nose and even allergies. It can act as a barrier for smell molecules to enter your nose, meaning you can’t physically pick up the smell.
These types of conditions can cause a progressive loss of smell, too. You may notice a gradual decrease in your smelling abilities over a span of several years due to the built-up inflammation in your nose.
This type of smell loss is actually the easiest to treat, Tajudeen explains, because doctors are able to treat the inflammatory condition, enabling you to regain your sense of smell.
What if you lose your smelling senses overnight?
Tajudeen says that a sudden loss of smell can mean a viral condition is at play.
“Usually when people have a cold, they have congestion and a runny nose, and they can’t breathe through their nose,” he says. “At the base level that usually causes a temporary reduction in smell. However, once the congestion resolves, in patients with viral induced smell loss, their smell does not recover.”
While most cold viruses cause congestion, other viruses can actually affect the olfactory sensory neurons in the nose. These neurons detect and send odorant information to the central nervous system. When a virus attacks these neurons, it can trigger a sudden, complete loss of smell, a condition referred to anosmia.
This sudden smell loss usually happens after you experience a severe cold, once your other cold symptoms have cleared up. It can result in a loss of smell that lasts from 6 months to years; in some instances, it may even be permanent. Additionally, patients may report “phantom smells” such as smelling smoke or gasoline when not present or having altered smells.
How do I know if my smell loss is related to COVID-19?
While on its face, COVID-19-related smell loss and smell loss due to other viral infections may look the same, they are different.
Tajudeen explains that instead of attacking the olfactory sensory neurons, COVID-19 affects the neurons’ supporting cells. You obviously can’t see this happening, so the telltale sign is when the smell loss occurs.
With most viral infections, smell loss will occur after the other viral symptoms — the nasal congestion and runny nose — have come and gone. With COVID-19, smell loss one of the first signs of infection.
“Smell loss is actually an early sign of COVID-19 and usually occurs for those who have a mild form of the virus,” says Tajudeen. “Patients with smell loss are normally at home recovering and not admitted into the hospital or on a ventilator.”
If your first symptom is smell loss, that is a good indicator to get tested and quarantine.
Another major difference is the length of smell recovery. With other viruses, recovery could take months and sometimes even years. Smell recovery for COVID-19 patient usually takes about four weeks. Tajudeen suggests that this could be because COVID-19 affects supporting cells, which regenerate faster than olfactory sensory neurons.
Should I see a specialist for my smell loss?
Anytime you experience a loss of smell, whether it’s gradual or immediate, it’s a good idea to see an Ear, Nose and Throat (ENT) specialist to ensure you get proper treatment.
In progressive cases, Tajudeen says it’s important to see a specialist as early as possible. The more your smell continues to decline over time, the more challenging it can be to treat.
Tajudeen and the team at the Rush Smell Loss Program have a variety of treatments for those with progressive smell loss — including a therapy to help people retrain their smelling nerves.
For COVID-19 patients, Tajudeen suggests seeing a specialist if your smell loss symptoms persist for longer than a month.
“Most COVID-19 patients who have smell loss do recover their sense of smell within about four weeks,” says Tajudeen. “During a recent study, we looked at about 1,000 COVID-19 patients. Based off their own symptom reporting, about 78% of those with total smell loss had completely recovered their smell at around the four-week mark.”
While almost 20% of the patients Tajudeen and his team studied did not recover their smell after four weeks, he suggests this could be from a variety of factors that a specialist might be able to identify and address.
“If you’re still having issues after a month, you should definitely get evaluated,” he says. “We’ve seen people develop things such as sinus infections after COVID-19, which could be prolonging smell recovery.”
While smell loss can be scary, the good news is that help is available to restore your sense of smell if it doesn’t come back on its own. While it may take some time, and possibly treatment, in most cases you’ll once again be able to enjoy your favorite fragrances.
Source: Rush University Medical Center
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