Scientists are looking for ways to speed up the healing of the sense of smell. Three years after the COVID-19 pandemic, researchers have a better idea of ​​how many people are affected and how long it will last. But the state of science is far from rosy when it comes to ways to rewire your sense of smell.

A method called olfactory training, or olfactory training, has shown promise, but big questions remain about how it works and for whom. exists. The coronavirus isn’t the first disease that steals odors. However, new pressure from those affected by COVID-19 has put smell training and many other new treatments in the spotlight.

The pandemic has increased the focus on the loss of smell. “If we need to provide a ray of hope, COVID is driving science at an unprecedented speed,” said Valentina Palma, an olfactory researcher and assistant director at the Monell Chemosensory Center in Philadelphia. says. “But,” she warns.

nose attack

Smell may seem like an afterthought compared to sight and hearing. But losing it can have profound effects on people. “When you lose your sense of smell, the world really changes, usually for the worse,” says Palma. The smell of a baby’s head, buttery curry, or the sharp salty sea can all add emotional meaning to the experience. can also do.

As an otolaryngologist, Pires remembers deaf patients who lost their sense of smell due to COVID-19 and participated in a clinical trial he and colleagues conducted in smell training. She worked for a perfume company. Her sense of smell was essential to her work and life. “At her first meeting, with tears in her eyes, she said she felt like she wasn’t alive,” she recalls Pires.

Unlike cells that sense colors and sounds, cells that sense smell can replenish themselves. These cells, called olfactory neurons, are dotted with molecular webs that trap specific odor molecules in the nose. When activated, these cells send messages to the brain through the skull.

Olfactory neurons are exposed to environmental hazards because they are adjacent to the nose. “They may be covered in a small layer of mucus, but they’re sitting there, constantly bombarded with bacteria, viruses and pollutants,” says Steven Munger, a chemosensory neuroscientist at the University of Florida School of Medicine. in Gainesville.

It is not known exactly how SARS-CoV-2 damages the olfactory system. However, recent research suggests that the virus attack is indirect. The virus infects and kills supporting cells in the nose, called supporting cells, which are thought to help keep olfactory neurons happy and nourished by supplying glucose and maintaining a proper salt balance. That attack can inflame the olfactory epithelium, the layer of cells that lines part of the nasal cavity.

Over time, the inflammation subsides, allowing olfactory neurons to return to normal work, the researchers speculate. But for some people, this process doesn’t happen right away.

That’s where smell training comes into play.

nose training

One of the few therapies that exist, smell training is pretty simple, good old nose training. Four scents (usually rose, eucalyptus, lemon and clove) twice a day for a month he sniffs deeply for 30 seconds.

In one study, 40 people with anosmia improved their ability to smell on average from training compared to 16 who did not receive training, olfactory researcher Thomas Hummel and his colleagues reported in March 2009. reported to laryngoscope.

Since then, many studies have shown that it works for 30 to 60 percent of people who try it, says Hummel of the Technical University of Dresden, Germany. In his view, this method works for some people, but “it doesn’t work for everyone.”

One of the good things, says Hummel, is that it has no harmful side effects. That is the “attractive place”. But getting the workout right requires discipline and stamina. “This is a waste if you don’t do it regularly and give up after 14 days,” he says.

We don’t know how this technology will work in people who might benefit from it. It may be drawing people’s attention to faint odors. It may be stimulating the growth of replacement cells. It may strengthen several pathways in the brain. Data from other animals suggest that such training can increase the number of olfactory neurons, says Hummel.

Overall, this nose boot camp might be an approach people can try, but big questions remain about how it works and for whom, says Munger. “In my view, it is very important to have an open discussion with patients about the very high probability that this treatment will not lead to recovery of their sense of smell, even if they and their doctors feel it is worth trying. “I’m not trying to discourage people here, but I also think we need to be very careful not to make unreasonable promises.”

Olfactory training has no harmful biological side effects, but it can be frustrating if it goes wrong, Palma says. I’ve talked to a lot of people who say they did 10 minutes.’ I met other people in groups so we held each other accountable and we did that for 6 months. It didn’t work for me,” she adds.

beyond training

Other potential treatments are under scrutiny, including steroids, omega-3 supplements, growth factors, and vitamins A and E, all of which may help the nasal epithelium recover.

More futuristic treatments are also in the early stages of research. These include epithelial transplantation designed to boost olfactory stem cells, treatment with platelet-rich plasma to reduce inflammation and promote healing, and even an “electronic nose” that detects odor molecules to directly stimulate the brain. “It is included. This cyborg-scented system is inspired by cochlear implants for hearing and retinal implants for vision.

According to Palma, for many people, the sense of smell is only evaluated once the sense of smell has disappeared, and a recent study of about 400 people underscores this indifference. The majority of respondents (nearly 85%) would rather give up smell than sight or hearing. About 19% of respondents would rather abandon their sense of smell than their mobile phone.Findings “dramatically show the insignificant value people have to their sense of smell,” researchers wrote in March brain science.

As a doctor who treats the loss of smell, Pires has made the new discovery that he likes good smells. “Had been missing it for a while, so I appreciated it even more.”