Author profile picture

If you suddenly can’t taste or smell properly anymore, it could mean that you are infected with the coronavirus. Researchers at Wageningen University, Netherlands, are therefore now developing a special home test. “This will allow people to test whether they smell and taste better or worse, and follow how it develops,” says Sanne Boesveldt, associate professor at the Wageningen University Human Nutrition & Health Department. As soon as people lose their sense of smell or taste, they should immediately go into home isolation or quarantine to limit further spread of the virus. The home test will be available before the summer.

Many people who became infected with COVID-19 appeared to experience loss of smell and taste at an earlier stage. Initial reports about this appeared as early as March. There were cooks who could no longer taste garlic and people who no longer smelled the stench of a diaper or litter box or the scent of shampoo. British doctors warned that the loss of smell and taste might be a sign of corona infection. Doctors in other countries, such as China and Italy, also observed this phenomenon.

Major international research

There were already smaller studies showing that thirty to ninety percent of corona patients experience loss of smell and taste. However, these studies were carried out very differently from one another. In order to get a better picture, six hundred physicians and scientists from the Global Consortium for Chemosensory Research (GCCR) have now begun a major international study. Boesveldt coordinates the research for the Netherlands. Wageningen is unique in the Netherlands because the university studies taste, smell and nutrition together. Boesveldt is seen as the expert in this field.

This broad research may contribute to an earlier diagnosis. Anyone can help by completing the online questionnaire if they have recently had corona-like symptoms. The questionnaire will remain available online for a longer period of time. Boesveldt: “It is also interesting to follow the course of a second or third viral wave.

“It is becoming increasingly clear that loss of smell and taste can be one of the symptoms when people are infected with the coronavirus. There are now even cases known where that was the only symptom,” says Boesveldt.

Developing the test is no simple task. “It’s not yet that easy to find products that everyone in the world has in their kitchen cupboards or bathrooms. Sugar and salt are good. But acidic and bitter substances, like vinegar and coffee, are more difficult. For the scent test, for example, we want to use shampoo. Even though everyone has a different shampoo, the smell remains constant over time.”

Questionnaire in 20 languages

Together with other GCCR researchers, Boesveldt compiled a questionnaire. Anyone who has had corona-like symptoms in the past fourteen days can fill it out. Boesveldt hopes that people who have already tested positive for COVID-19 will also want to participate in the study. “We ask specifically about the duration and sequence of different symptoms and the longer it has been, the less people can remember the exact details,” Boesveldt explains.

In this way, the researchers hope to obtain a lot of information and gain a better understanding of the virus. For example, it is not yet clear exactly how early the loss of smell and taste occurs or how long it lasts. “When people have recovered, it seems to return,” says Boesveldt.

Loss of taste caused by loss of smell

She suspects that a corona infection only affects the sense of smell. In general, the perception of taste rests to a large extent on smell. “When people come to the Smell and Taste Center and say: ‘I don’t taste anything anymore,’ the taste system is still 95 percent intact. People experience loss of taste because the smell of food is gone.”

If we have a cold and a stuffy nose, it inhibits our sense of smell. But with COVID-19, something else seems to be happening. Boesveldt: “It seems that the coronavirus binds to a certain type of receptor that is very common in the nose. These are special cells that are sensitive to stimuli. We think that the virus attacks the tissue that contains the olfactory receptors that normally signal to the brain that smells can be detected.”