Your Sense of Smell Can Return After COVID—But It Can Get Weird

One of the hallmarks of a COVID-19 infection is the loss of the sense of smell (anosmia). It is the main neurological symptom of COVID, affecting about 90% of patients with the virus. Experts say that loss of smell might be a better predictor of COVID infection than other symptoms of the illness.

What does it mean if someone with COVID or another viral infection loses their sense of smell? Will it come back? And if it does, will it be the same as it was before?

Viruses and Sense of Smell

Eric Holbrook, MD, an associate professor of otolaryngology and head and neck surgery at Harvard Medical School and division director for rhinology at Massachusetts Eye and Ear at Massachusetts General Hospital, tells Verywell that other viruses besides COVID can cause anosmia.

“Post-viral smell loss was a known entity,” says Holbrook. “We were unable to directly identify what viruses caused it mostly because these patients would come in long after the acute symptoms and so it’s very hard to detect what virus actually caused it.“

People may lose their sense of smell when they have stuffed up sinuses from a cold or the flu. While it can be temporary, some people will notice that their sense of smell has not come back after the nasal congestion clears.

Holbrook specializes in treating disorders of the senses of smell and taste and says that “around 40% of the patients that would come to see me had this history of having a cold, and then losing their sense of smell.” It’s also possible for people to suddenly lose their sense of smell after a head injury.

Coronaviruses other than SARS-CoV-2 can also cause the loss of the sense of smell. Holbrook says that anosmia was reported with some cases of the coronavirus that caused the outbreak of severe acute respiratory syndrome (SARS) in 2003 and 2004, but that the symptom was “not nearly as prevalent as it is with COVID-19.”

Holbrook says that researchers were “a bit clued in” with COVID-19 because the loss of the sense of smell was reported early in Europe—which was hit by the pandemic before the United States.

“If you have a normal sense of smell, and you suddenly lose it, you really notice it,” says Holbrook. “The combination of smell and taste is what gives you a sense of flavor in food.”

People who have a more progressive loss of the sense of smell—which can happen with age—may not be as bothered by it because the gradual loss allows them to become accustomed to the change.

While some people with COVID-related anosmia recover within a few weeks, many people may take longer to recover. One study found that about 95% of people recovered from COVID-related anosmia within six months.

What Causes Loss of Smell?

The structures that make up the sense of smell are located in the roof of the nasal cavity, behind the nose, just in front of the brain. The olfactory sensory neurons detect molecules in the air that are connected to the substances around us, which are then connected directly to the brain. Odors reach the neurons both through the nostrils and the mouth.

When the coronavirus started affecting patients’ sense of smell, the worry was that the neurons were affected, suggesting that other neurological problems could be occurring.

Sandeep Robert Datta, MD, PhD, a professor of neurobiology at Harvard Medical School, tells Verywell that what was actually happening was that the sense of smell was impaired by SARS-CoV-2 when it attacks the cells that support the neurons in the nose (which sense odors) rather than an attack on the sensory neurons themselves.

Datta and his colleagues found that the sensory neurons do not have a receptor protein called ACE2 (which the SARS-CoV-2 virus uses to break into human cells). However, the cells that provide support to the neurons do have the protein—which is why the virus can attack them.

Holbrook says that the research suggests that damage to the sense of smell and the association of having smell loss with COVID-19 is probably related to the inflammation that occurs around the sensory neurons but not necessarily directly infecting them to cause damage.

Why Smells Might Be Weird After COVID

Since the sensory neurons are not affected, the lost sense of smell that can occur with COVID is unlikely to be permanent. The olfactory sensory neurons and other cells can regrow—which Holbrook says means that, unlike vision or hearing loss, the sense of smell can be regained.

However, the recovery of the sense of smell—which does not always happen—can have missteps along the way. The nerves grow slowly and have to reconnect to the brain, and those new connections may have a shakedown period during which they do not function well.

Holbrook says that parosmia—where what you experience as a smell does not match the actual odor—can also happen. For example, a sniff of a rose ends up being experienced as a whiff of skunk. Curiously, the wrong sensation will usually be a bad one rather than a good one—a rose might smell like a skunk but not the reverse.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.