Why the loss of smell with Corona sometimes persists - and what you can do about it

Created: 01/04/2023, 08:30

By: Yannick Hanke

Sometimes the loss of smell after a corona infection lasts longer.

But why is that?

© Christina Horsten/dpa/imago/Montage

Loss of smell can occur after a corona infection.

For some people, this persists.

But why?

And what can be done about it?

Berlin – You smell and taste nothing or hardly anything anymore?

Everything suddenly tastes like a lump of cardboard?

This can sometimes be attributed to a corona infection.

After being infected with Covid-19, people in Germany alone have reported in large numbers that they have noticed changes in their sense of smell and taste.

Meanwhile, about three years after the outbreak of the global pandemic, the loss of smell is considered a typical symptom of a corona infection.

For some, it can last weeks or even months after infection.

Now a US research team has found the possible cause of the ongoing loss of smell.

Loss of smell continues after corona infection: study from the USA investigates the reason

The researchers say that it is not the coronavirus itself that would damage the cells in the nose, but your own immune system.

For this finding, the researchers examined the olfactory mucosa of those affected and discovered inflammatory processes there.

These would have continued even if the virus had long been undetectable.

"This thorough study provides evidence that persistent olfactory disorders are associated with inflammation of the olfactory mucosa," explains ENT specialist Thomas Hummel from the University Hospital Dresden to

.

"It has never been shown before," says Hummel, who was not involved in the work.

Peter Berlit, Secretary General of the German Society for Neurology (DGN), also speaks of a "very valuable insight".

Olfactory dysfunction is one of the most common symptoms after a corona infection

According to the team of authors led by Bradley Goldstein from Duke University in Durham (USA), olfactory disorders are among the most common symptoms of Covid 19 disease.

This finding was published in the journal

.

It is already known that the coronavirus can have a direct impact on the olfactory mucosa.

This means the three to five square centimeter small area that lies deep in the nasal cavity in the upper nasal passage on both sides of the nasal septum.

It contains about ten million olfactory cells as well as supporting and stem cells.

Previous studies - for example from the Max Planck Institute for Neurogenetics in Frankfurt - had shown that the coronavirus in the mucous membrane does not infect the actual olfactory cells, but the neighboring supporting cells that supply the olfactory cells with nutrients.

Apparently, the supporting cells recover in most patients with Covid-related olfactory loss.

The loss of smell is therefore only temporary.

Why does the loss of smell after a corona infection persist in some people?

The question that has remained unanswered so far: What happens to people whose olfactory disorders last longer?

To answer this question, the team analyzed mucosal samples from a total of 24 people.

Nine of them suffered from prolonged loss of smell after a Covid disease.

During their investigation, the researchers then came across T cells, among other things.

These are associated with inflammatory reactions.

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And: These inflammatory reactions continued even if the actual infection was a long time ago.

In addition, there were noticeably few olfactory cells in the tissue.

Perhaps their numbers had dropped as a result of the ongoing inflammatory response.

But the researchers also admit that their guesses are based on only a small number of samples.

I would have liked a larger number of cases.

ENT specialist Thomas Hummel from the University Hospital Dresden on the smell loss study

"I would have wished for a larger number of cases," says ENT specialist Thomas Hummel.

Because then one could also have checked whether, for example, the age of those affected plays a role in the loss of smell.

Finally, olfactory disorders tend to last longer in older people.

Nevertheless, DGN Secretary General Peter Berlit considers the conclusions of the study to be plausible: "You can easily conclude that from the data."

How persistent loss of smell after a corona infection can be combated

However, the researchers' study does not only get to the bottom of the cause of the persistent loss of smell after a corona infection.

It also provides pointers to possible treatment options.

This could inhibit immune cells that promote inflammation.

According to the team of authors, appropriate medication could be applied to the olfactory mucosa via the nose.

According to ENT doctor Hummel, anti-inflammatory drugs such as steroids or platelet-rich plasma could be used to improve the olfactory disorders.

Although the success rate of such therapies for corona-related odor loss has been modest to date, they may be suitable for certain patients.

Great chance of the sense of smell returning after a corona infection - within a year

Meanwhile, Berlit refers to a

study from the Netherlands published in the journal

Here, tablets with the cortisone preparation prednisolone would not have brought any improvement in people who had suffered from olfactory disorders for more than four weeks.

Against the background of the new findings, Berlit believes it makes sense to now examine the direct application of cortisone to the olfactory mucosa.

In principle, the chance of a return of smelling within a year is very high, according to neurologist Berlit.

But there is still no drug therapy with proven effectiveness.

What could encourage those affected: In the summer of 2021, researchers from France published

figures in the context of the duration of olfactory disorders in the specialist journal

About 84 percent of the 51 participants affected by smell loss had fully regained their sense of smell after four months.

And by the end of the study, 12 months later, 96 percent of the subjects had regained their sense of smell.