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Advances in Care

The Loss of Smell Due to COVID-19

A Very Common But Mysterious Symptom

Published February 2021

It is estimated that 80% of patients infected with SARS-CoV-2, the virus that causes COVID-19, experience a loss of smell. Although it is a seemingly harmless symptom, it could be a sign of a larger problem.

Three percent of people in the U.S. already live with either a minimal sense of smell or anosmia, the permanent loss of ability to smell. If you are one of the many people who have experienced a loss of smell as a result of getting COVID-19, here are a few answers to frequently asked questions.

Should I take this symptom seriously?
Yes. It is a sign you might have a serious infection. "This should trigger you to act responsibly, get tested and quarantine until you can prove you don't have COVID-19," advises Michael G. Ison, MD, infectious diseases and organ transplantation specialist at Northwestern Medicine. Additionally, the loss of smell leaves you more at risk for danger if you can't smell smoke from a fire, spoiled food, chemicals or other odors in your home.

Why does the loss of smell happen?
The medical community does not fully understand, but researchers are testing some theories. According to a study conducted at Harvard Medical School, smell nerve cells in the upper nasal cavity (also referred to as support or stem cells) are very vulnerable to SARS-CoV-2 and are likely what is infected by the virus, causing the loss of smell. Although olfactory and sensory neurons, which identify and transfer scents to the brain, may still be affected by the SARS-CoV-2 virus, this study disproved the theory that these neurons are the most vulnerable to the SARS-CoV-2 virus. Another study suggests the loss of smell associated with COVID-19 could be linked to inflammation and bleeding in the olfactory bulbs, the part of the brain that controls your sense of smell.

How does the loss of smell affect my taste and food cravings?
Your sense of smell and taste are intertwined. So, a loss of smell is often associated with a loss of taste. Although less research exists to explain why getting COVID-19 decreases patients' ability to taste, it is most likely related to the loss of smell. This can completely affect how you perceive the world.

How long does the loss of smell last?
"Many of the patients I've seen will notice that their sense of smell comes back, but it does so slowly. They often say they have a persistent dullness for some time as well — they can smell, but they don't smell as brightly as they could before getting COVID-19," states Dr. Ison. The average duration of experiencing a loss of smell is eight days, but some patients have reported not being able to detect odors for weeks or even months. Others have reported registering certain odors and tastes differently when recovering their sense of smell after having COVID-19.

Could I lose my sense of taste and smell after receiving the messenger RNA (mRNA) COVID-19 vaccines?
No. You cannot experience this symptom after receiving the Pfizer-BioNTech or the Moderna COVID-19 vaccines because they do not give you COVID-19. The mRNA vaccines deliver a version of the COVID-19 genetic code to your cells. These vaccines do not contain the SARS-CoV-2 virus, so there is no way for you to get infected through vaccination.

How can I test my sense of smell?
Grab a collection of items with an identifiable smell, such as coffee beans, garlic or a strongly scented candle. While closing your eyes, try to identify each item as someone in your household places the items under your nose. If you are having issues identifying the item, you may be experiencing a loss of smell and should consult your physician. Your loss of smell may be related to COVID-19 or other medical conditions.

Michael G. Ison, MD
Michael G. Ison, MD
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