But in February 2022, a study published in the journal Cell looked at COVID-19-infected hamsters and human tissues to explain what experts refer to as “olfactory dysfunction,” or the impaired ability to detect scents. What they found—and this is a shocker—is that COVID-19 doesn’t actually infect the nerves responsible for detecting the smell of cookies in the oven or a scented candle aglow. “SARS-CoV-2 only enters the nerve cells in exceedingly rare situations,” says study co-author Dr. Jonathan Overdevest, MD, assistant professor of rhinology and skull base surgery at New York-Presbyterian/Columbia University Irving Medical Center. “The smell loss that is experienced acutely in COVID-19 is likely due to the loss of olfactory receptors on these nerves.” Typically, olfactory receptor cells surround and support olfactory nerves by changing scent molecules from fat-soluble to water-soluble so they can be washed away and make way for new incoming scents, says Dr. Sam Huh, MD, chief of otolaryngology at Mount Sinai Brooklyn Hospital. However, when COVID-19 strikes, it kills these support cells, leading to an inflammatory immune response in the area. This response may be an evolutionary adaptation designed to prevent the virus from entering the brain, study co-author Stavros Lomvardas, PhD, told The New York Times. As a result, freshly baked cookies and candles may go unnoticed—at least for a while. The interruption in regularly scheduled sniffing also messes with sensations in your mouth: “We know that smell is integral to the way that we perceive the flavor of foods, at times more important than taste,” says Dr. Overdevest.
The implications
The findings explain why most COVID-19 patients find their sense of smell and taste ultimately return: After all, if it COVID-19 were to infect and kill the olfactory nerves themselves, you’d never recover your senses and be much worse for the wear. “Patients who’ve lost their taste and smell really suffer,” Dr. Huh says. “They don’t want to eat, they lose weight, and they become depressed since smells play such a big role in the formation of memories.” In reality, when COVID-19 is the culprit, your sense of smell can and should eventually return once inflammation lets up and the olfactory receptor cell regenerate. Anecdotally, this can take anywhere from a few weeks to eight months, according to Dr. Huh. But because COVID-19 isn’t always the culprit when one’s sense of smell goes kaput, it’s smart to get loss of smell checked out rather than wait and hope. After all, a brain tumor or polyps in the nose could also impact your sense of smell, Dr. Huh warns. At the very least, an ear, nose, and throat doctor may recommend scent training, one way to help you recover your senses: Three to four times a day, you’ll sniff and taste five-strong odors like citrus, vanilla, cloves, coffee, and cinnamon. Dr. Huh is a fan: “It seems to work pretty well in expediting the return of how you used to smell before.” Next up: Here’s What You Need to Know About the Long-Term Effects of COVID-19
Sources
Dr. Jonathan Overdevest, MD, assistant professor of rhinology and skull base surgery at New York Presbyterian/Columbia University Irving Medical CenterDr. Sam Huh, MD Chief of Otolaryngology at Mount Sinai Brooklyn HospitalThe Association Between Olfaction and Depression: A Systematic ReviewAnosmia and dysgeusia in SARS-CoV-2 infectionNon-cell-autonomous disruption of nuclear architecture as a potential cause of COVID-19-induced anosmia
