Smell loss can occur in anyone infected with a cold, but it has been a particularly common symptom of COVID-19. Depending on the study, research suggests that anywhere from 19–85 percent of individuals with COVID-19 infection experience impaired smell.
Of course, the numbers are changing due to new variants. Early data from the U.K., which experienced the Omicron spike ahead of the U.S., indicates that the Omicron strain may be less likely to cause smell loss. Patients reported a loss of smell or taste in 35 percent of Delta cases and 13 percent of Omicron cases. Yet that’s still a significant number of people being impacted.
Fortunately, most individuals who lose their sense of smell due to a virus get it back—and fairly quickly. One of the amazing things about olfactory neurons is that they can regenerate. The vast majority of people recover their smell within a month. For a few it can take up to a year.
Smell loss lasting more than a month needs attention
A small number of individuals who lose their sense of smell due to viral infection may have trouble getting it back. Anyone who hasn’t recovered their sense of smell after a month should consider seeing their doctor, who can refer them to an Ear, Nose & Throat (ENT) specialist.
Smell loss is a serious concern. It makes it difficult to identify hazards such as smoke and natural gas. It puts people at higher risk of food poisoning. It also brings new challenges to caregiving, since people commonly rely on their noses to figure out when diapers need changing. There are social consequences as well. Without smell, people may put on too much perfume or fail to notice their own body odor.
Smell has a tremendous impact on quality of life since so much of what we perceive as taste is actually smell. People who experience smell loss generally struggle to cook and enjoy food. For individuals such as chefs, the loss can have occupational consequences.
Scratch-and-sniff testing helps evaluate severity
In our ENT department at Vancouver Clinic, we use the University of Pennsylvania Smell Identification Test to determine how severely an individual’s sense of smell has been affected. It’s essentially a 40-question scratch-and-sniff assessment. Patients’ results are compared with other individuals of the same age and gender to determine if the smell loss is mild, moderate, severe, or complete.
We also ask questions and can do an exam to check for nasal polyps. Natural aging, as well as injuries and diseases—for example, sinus inflammation, an obstruction, and neurodegenerative conditions—can also cause smell loss.
Olfactory training using essential oils helpful
In terms of treatment, there is high-level evidence that olfactory training helps. By slowly and intentionally smelling four different essential oils twice a day for six months, some patients are able to retrain their brains and make new neural connections to their noses. I typically recommend eucalyptus, clove, citrus, and floral oils due to their strong and unique scents.
In a few cases, patients might experience parosmia, which is a distorted sense of smell. Imagine coffee smelling of paint or wet dog. Parosmia can make it challenging to eat and perform daily activities. Yet the silver lining is that distorted smell can be evidence that the body is trying to recover neural connections—it just isn’t happening the right way. Olfactory training may help with this condition too.
Talk to a doctor instead of eating burnt oranges
What is unlikely to help either condition is the burnt orange “hack” prevalent on social media. There is no evidence that smell can be recovered by consuming certain types of food. Instead, it’s best to consult a physician and use evidence-based treatment, rather than delaying recovery by focusing on unscientific approaches.
If you have questions about smell loss, I encourage you to reach out to your primary care provider. He or she can refer you to a specialist if you need additional care.
Dr. Nancy Liu is an ENT doctor at Vancouver Clinic. She cares for adults and children of all ages.