How is it diagnosed and how long can loss of smell last in long covid?

How is it diagnosed and how long can loss of smell last in long covid?

Covid-19 can affect people in different ways, including some individuals who may have the disease completely asymptomatic. However, this is not the rule for everyone, and loss of smell (called anosmia) or even a reduction in the ability to smell (hyposmia) is quite common in infected people. Unfortunately, the olfactory problem can remain for months, and is considered a symptom of long-term covid.

  • Covid long | Everything you need to know about the condition
  • Vaccinated are 40% less likely to develop long-term covid

Observing the outcome of people who develop loss or changes in smell, it is possible to state that most will recover it in a few weeks. But there are some exceptions, according to researchers at the Karolinska Institutet in Sweden.

The team found that, 12 to 18 months after the initial diagnosis of covid-19, 34% to 46% of people may still have some clinical reduction in olfactory functions, as a sequel to the acute phase of the disease. Despite the high percentage, most people are not aware of the problem, especially when it is less obvious.

How to discover loss or changes in smell?

If the person develops anosmia, the diagnosis of loss of smell is obvious, as the individual will not smell a perfume or the food they consume. The main diagnostic challenge occurs when the changes are more subtle. Here, it should be noted that some people may develop phantosmia, a type of olfactory hallucination. In these cases, instead of smelling freshly brewed coffee, it identifies an odor of gasoline, for example.

Inside the office of an otorhinolaryngologist, some tests can be performed to measure the intensity of the olfactory loss. The most traditional is olfactometry, also known as smell assessment, which consists of using bottles with scents or papers with microcapsules that contain fragrances. After being exposed to scents, the patient must identify which smell they feel.

With technology adapted from the perfumery market, the Brazilian startup Noar has a digital scent device that works connected to a tablet. Without the need for flasks or papers, the tool releases fragrances through dry air technology.

According to the startup, the fragrance is released, leaving no residue in the air, on the demonstrator or on the user. This allows for more scent testing, without compromising and cluttering up the environment with a mixture of essences. Finally, the test results are sent simultaneously, virtually, facilitating the diagnosis.

Smell training can be a good strategy

After identifying the problem, the best way to accelerate the improvement of smell capacity is from smell training, according to the National Health Service (NHS) in the United Kingdom. Basically, the person should smell different “fragrances” and try to associate them with their name.

“The sooner you start smell training, the more it can help,” says an NHS article. However, the activity is only valid for those who can already distinguish at least two smells, even if they don’t know what they are.

Among the scents recommended for starting therapy, British specialists advise using materials that already exist at home and are familiar to the patient, such as:

  • Coffee;
  • Perfumes;
  • citrus fruits;
  • Essencial oils.

Other diseases can cause loss of smell

While olfactory loss seems to be something unique to covid-19 and long-term covid, this is not exactly true. “The olfactory loss can be caused by other viruses or infections, head trauma or a series of neurodegenerative diseases”, comments Johan Lundström, from the Karolinska Institutet, in an article for The Conversation website.

To avoid the risk of parosmia in the context of the pandemic, the 100% effective solution is not to contract the SARS-CoV-2 coronavirus infection. However, being vaccinated and having received booster shots can significantly reduce an individual’s risk of developing long-term covid, according to scientists from the British Institute of National Statistics.

Source: The Conversation, NHS and MedRxiv