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What is smell training? Experts suggest it could help COVID-19 long-haulers

Loss of smell and taste is more common with COVID-19 than with any other viral disorders, but experts say there is something people can do to help.
Smell training could help to reignite senses dulled or lost due to a COVID-19 infection.
Smell training could help to reignite senses dulled or lost due to a COVID-19 infection.TODAY Illustration / Getty Images
/ Source: TODAY

When Jennifer Sopko contracted COVID-19 at the end of December, she experienced mostly mild symptoms, a little congestion, a little sniffling and a headache that would “come and go.” By the fifth day, though, she lost her ability to smell. On New Year’s Eve, she ordered takeout and noticed her boneless wings didn’t exactly taste right.

“Whenever I would smell them, you know that Buffalo sauce, it was like a sharp, weird sensation in my nose. I knew something was happening,” the 38-year-old historian and writer in Pittsburgh told TODAY. “It’s really the most bizarre experience. It’s difficult to describe to somebody who hasn’t gone through it.”

A few weeks later she thinks she has some of her smell and taste back, but it’s not what she remembered.

“I don’t think I’m really tasting the flavors of food or smelling them,” she said. “I was eating a bowl of chicken noodle soup. I couldn’t taste the flavor, but my tongue could tell that it was salty.”

COVID-19’s impact on smell and taste

Sopko is not alone. Experts believe a majority of people with COVID-19 will experience “some measurable olfactory disfunction.”

“It is more common with COVID than with any other viral disorders. It is often the case that many people will lose their sense of smell and they'll say their sense of taste,” Pam Dalton, a faculty member at the Monell Chemical Senses Center in Philadelphia, told TODAY. “But, generally, it’s the flavor that gets diminished when you lose your ability to smell.”

Anyone who has had a bad cold knows that it can affect smell and taste. But the reasons why differ. When people lose their ability to smell when grappling with a sinus infection or cold, it’s often because the mucous prevents the nose from doing its job.

“Some of that with the common cold is really due to nasal congestion,” Dalton explained. “The molecule simply can’t make it into the nose where the receptor is.”

But what happens with COVID-19 appears different: Experts believe that it targets the neurons responsible for smell.

“Infection and loss of function of the supporting cells leads to loss of the olfactory sensory neurons,” Dr. Claire Hopkins, a professor of rhinology at King’s College London, told TODAY via email. “Fortunately, these have a unique capacity in the nervous system to regenerate — and most patients will still recover but it can take months for this to happen.”

But for those like Sopko or Avery Brennan, 18, not being able to smell is frustrating and upsetting.

“Oct. 3, I tested positive. I lost my taste and smell three days after,” the freshman at the University of Florida in Gainesville, told TODAY. “I don’t know how to describe it. It’s like I have this one taste in my mouth that when I eat food everything tastes like that. Everything smells like that. It’s kind of just a bitter taste.”

Hopkins said while this might be distressing, it could be a positive sign.

“Many people who lose their sense of smell develop parosmia during their recovery, a distorted sense of smell, which is often foul or unpleasant. We think this reflects the recovering sensory neurons working incorrectly,” she said. “In general, it is a positive predictor for long-term recovery, but can last for months and can have a major impact on appetite and quality of life.”

Smell training offers hope

People who lose their sense of smell can help bolster their senses by trying something called smell training, which involves people sniffing scents to spark the sense. Dalton said about a dozen papers looked at smell training pre-COVID-19 and found it works.

“Smell training is actually effective,” she said. “There was just a recent study of therapies for post-viral olfactory loss. Of all the things that they looked at … the only thing that they recommended was smell training.”

Researchers have examined other therapies — including vitamin A, omega-3 supplements, antibiotics or various steroid treatments — with mixed results. Smell training remains easy to do at home with an added expense: Dalton recommends people pick four or five different scents that smell different but are easily recognizable.

“You need to remember what it smelled like before you lost your ability to smell. That’s very helpful,” she said. “You can pick your shampoo. You can pick a fragrance that you like. You can go into your kitchen cabinet and pull out some spices.”

How to regain sense of smell after COVID-19

Hopkins, who has been working with the British nonprofit AbScent, an organization providing support for anyone affected by anosmia or smell disorders, says that research shows that four scents work well:

  • Rose
  • Lemon
  • Eucalyptus
  • Clove

“(They) cover four of the main groups of different smells,” she said. “You can use other things — but coffee is a common trigger for parosmia and might not be ideal.”

Dalton recommends people smell each scent for 10 seconds with a “couple of slow, deep breaths” while thinking about what they’re trying to smell. AbScent recommends people do this twice a day for four months. Smell has a strong relationship with memory so pondering how lemons smell while imagining their scent bolsters the process.

“Smell and memory are very tightly linked in the cortex, the part of the brain that deals with emotion and memory. It is actually physically connected to the primary olfactory processing areas,” she said. “The phenomenon about smelling something and feeling like you’ve been taken back on a trip through time … is a very common experience.”

Hopkins agrees. “Smells can evoke really strong memories,” she said. “One of the greatest losses reported by some of my COVID patients is being unable to smell their newborn babies.”

The one thing Brennan can smell is the perfume she wore for years. But that could be because she has such a strong memory of it.

“I wore it every day,” she said. “I don’t know if it is just because I wore it so consistently, but for some reason that’s the only scent I can smell.”

While people feel distressed that they can’t smell or only smell and taste something foul or metallic, there is hope. The experts believe people can recover their smell, it just might take time.

“That can be really tough for patients, as losing sense of smell has a significant impact that can be hard to understand,” Hopkins said.