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Why does the coronavirus make you lose your sense of smell?

loss of smell coronavirus symptom
Photo via Dennis Wong/Flickr (CC BY 2.0)

In the early days of the coronavirus, one symptom became a clear sign of likely infection: the loss of the ability to smell.

It wasn’t immediately clear why olfactory capacity is affected by the coronavirus, outside of the disease’s targeting of the respiratory system. However, new research shows that this particular symptom of COVID-19, aka anosmia, affected at least half of COVID-19 patients who’ve received official diagnosis. Those patients had full-blown anosmia caused by the disease’s interaction with the central nervous system. 

Despite similarities to loss of smell which comes with a common cold, COVID-19 patients have been shown to have much more profound loss of smell, with a weaker ability to identify smells and to taste bitter or sweet flavors. Similarly, COVID-19 can also cause depressed moods and other psychological symptoms not immediately associated with what has been conceptualized as a respiratory illness. 

One professor, Carl Philpott from the University of East Anglia in the U.K., gathered 30 volunteers for a smell and taste test. Ten of them suffered from COVID-19, ten of them had a bad cold, and 10 didn’t have any cold or flu symptoms. According to him, the coronavirus patients had a smell loss that was much greater than the other two groups.

“There really do appear to be distinguishing features that set the coronavirus apart from other respiratory viruses,” Philpott said, via the BBC. “This is very exciting because it means that smell and taste tests could be used to discriminate between COVID-19 patients and people with a regular cold or flu.”

While it’s not immediately clear how the virus affects the central nervous system, anosmia without significant nasal congestion or swelling suggests it does not come from blockage or pressure.

For those who do experience a loss of smell, research from the University of Alabama – Birmingham shows that there is a 60-80% chance of regaining olfactory capacity through retraining. The value of smell to not only cooking and eating, but also safety, means that returning to a previous state of olfactive function is incredibly important. 

Sources: STAT News, Medical Xpress, Science Daily, University of Alabama


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