Researchers studying COVID-19 have known for a while that loss of taste and smell are among the most common symptoms (except with the new Omicron variant). But with a few more studies now digging into the connection, there are more clues to why it happens and how it can be treated.
Why does COVID-19 cause loss of taste or smell?
One possible way is that the virus could damage the cells in the olfactory epithelium, which is a patch of skin containing smell receptors that convert stimuli into signals for the brain. Another is that it might disrupt the neurons that help send those signals to the brain. Or, it could affect the taste buds directly. Researchers also point to inflammation around the nose and mouth caused by an immune response as a possible trigger for smell or taste loss.
Still, more research is being done on why some people with COVID-19 lose these senses while others don’t. This week, researchers from the DNA testing company 23andMe published a paper in Nature Genetics suggesting that those infected with the virus who possess a certain genetic locus were 11 percent more likely to lose their sense of taste or smell. The genes they pinpointed play a key role in processing smells.
How seriously does COVID affect smell and taste?
By combing a Facebook support group, medical researchers from the UK found that individuals whose smell and taste were altered due to COVID-19 experienced significant physical and psychological effects, including decreased pleasure in cooking and eating, weight fluctuations, poor emotional well-being, and difficulties with social bonding.
Although most patients recovered their sense of taste and smell in a few weeks, about 10 percent had persisting symptoms like parosmia, which can distort familiar odors for a person. Some with parosmia report that scents that normally appear sweet or pleasant can smell rotten or foul. According to the study authors, those with persisting changes in taste or smell can feel as if they have an invisible illness, which leads to isolating thoughts.
If this sounds like you, there are ways to partially regain pleasure in eating. A group of food scientists from Brazil suggest that eating things that are brightly colored or crunchy can result in a more satisfying experience, due to the interplay of other senses like touch and sight.
Do smell and taste come back after COVID?
The good news is that most people eventually recover their sense of taste and smell once the virus dies away in their body. A team of interdisciplinary experts from Italy surveyed patients with chemosensory dysfunction (a fancy way of saying alteration or loss of the senses) a year after infection. Of the 268 respondents, almost 70 percent reported some chemosensory dysfunction while infected with COVID-19. A year later, only about 21 percent reported that they hadn’t fully regained smell and/or taste.
In addition, researchers at the Virginia Commonwealth University School of Medicine found that those with nasal congestion at the time of infection were more likely to recover their sense of smell, while those with difficulty breathing or prior head trauma were less likely to recover their sense of smell.
Meanwhile, others are working to help patients recover their taste and smell. A group of scientists from the Tabriz University of Medical Sciences in Iran have suggested some possible solutions, including vitamin A supplements and insulin administered through the nose. But they also note that more clinical trials are required to investigate those treatments before people start asking their doctors about them, or worse, trying them at home.