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Can You Train Your Senses to Smell Again After COVID-19?

26 March 2022

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The next time you sit down for a meal, think of the complex process that occurs for you to savor and enjoy your food. It’s common to associate your taste buds with flavor, but your sense of smell is actually what contributes the most to how you experience food – it is believed some people can smell anywhere between 10,000 and 100 billion types of odors.

Considering a loss of smell is one of the most common symptoms associated with COVID-19, this explains why your appetite can suddenly decrease when you’re sick with a respiratory infection. Research during the pandemic points to mostly positive news when it comes to a loss of smell, with 90 percent of people seeing their smell improve within one to four weeks and 95 percent of people recovering by six months.

However, there is a remaining subset of people who experience reduced, distorted or a total loss of smell. Although a clinically-approved method has yet to be developed to treat a loss of smell after COVID-19, we’ll explain why olfactory training can be helpful in speeding up the smell recovery process.


What causes a loss of smell?

How the brain interprets various smells is one of the more fascinating parts of the human body. Whether it’s from food or from something in nature, what you smell comes from tiny odor molecules that stimulate olfactory neurons in your nose. These neurons then send a specific coded message to your brain of what you’re smelling. This is an oversimplified description of how smelling things work. In reality, there are millions of olfactory neurons, each one responsible for producing a specific type of odor receptor. 

Once inside the nose, the neurons send a message to the olfactory bulb, an area of the brain where the process of what you smell begins. From there, a message is sent to the piriform cortex for further decoding.

As you can see, this is a complex process. Any type of interference can alter what you smell. For example, viral infections, such as the flu or COVID-19, create inflammation as part of your body’s immune system response. This inflammation is what creates body aches and congestion in your nose. That same congestion can impact how your brain receives signals of what you’re smelling.

When COVID-19 appeared, many people experienced an acute version of hyposmia (decreased sense of smell) or anosmia (inability to smell). Some people also experienced phantosmia (smelling odors that aren’t there) and parosmia (smelling strange odors). These symptoms typically improve as time goes on, usually after weeks or months.

However, direct damage to olfactory neurons isn’t the culprit for COVID-related loss of smell. Instead, the virus impacts support cells – called sustentacular cells – around the neurons that prevent the olfactory system from sending messages from the nose to the brain. The cells aren’t dying, rather nasal inflammation overloads sustentacular cells to a point where their attention is diverted away from the smelling process. As the inflammation diminishes, smell returns.


Olfactory training

Think of olfactory training as physical therapy for your nose. Olfactory training, also known as smell retraining therapy, involves smelling familiar odors to stimulate and re-engage your sense of smell. It was first developed in 2009.

Over time as nerves regrow, smell training encourages improved brain connectivity by focusing on memories and experiences while you smell foods and scents.

Choose which scents you want to smell at your own discretion. However, you should stick to scents from four categories:

  • Fruity
  • Spicy
  • Floral
  • Resinous

Much like how your taste buds identify certain flavor profiles – salty, sweet, bitter, sour and savory, your nose also differentiates certain smell categories such as floral, fruity, spicy, resinous, sweet, pungent, chemical or decayed. Because smelling chemicals (bleach) or decayed items (rotten food) aren’t advised, olfactory training focuses on more enjoyable scents such as lemon or rose.

Smell these scents for 10 to 20 seconds once or twice a day. With each scent, focus on your memories of that smell. For example, when smelling lemons, think of lemonade you used to drink as a child or lemon bars you used to eat for dessert.

Just as physical therapy for a knee injury can take months to recover from, smell training can also take time. Patience is key to avoiding frustration. Smell training typically lasts for at least three months.


Smell training after COVID

While most COVID-19 cases resolve in several days or a week, some people suffer from long-COVID symptoms that can include a more chronic loss of smell. In fact, a 2021 study found as many as 1.6 million people suffer from chronic olfactory dysfunction.

To date, there isn’t an approved treatment for COVID-related loss of smell. However, smell training is recommended by the American Academy of Otolaryngology–Head and Neck Surgery and has been touted by the chief medical officer of the Centers for Disease Control and Prevention. This is because there are no side effects to performing smell retraining therapy. While its effectiveness may vary from person to person, there isn’t any harm in trying.

Smell training after COVID involves picking four scents or fragrances and smelling them twice a day for several months. You can switch out the scents after several weeks and try new ones.

Essential oils for COVID smell training

Using a store-bought orange or flower is an easy way to start the smell training process. You can also buy essential oils to smell. Essential oils are a concentrated version of a scent, meaning they may help you better identify and remember smells due to their strength. Plus, essential oils don’t spoil or go bad like foods can.

Popular essential oils for this form of treatment include lemon, rose, clove and eucalyptus. You can even find essential oil starter kits online to use for your smell training.
To use essential oils in your smell training, place several drops into a small jar with a lid. Open the lid and inhale the scent for 20 seconds, then close the lid for your next use.


Myths about how to treat COVID loss of smell

Whether on TikTok, Facebook or other social media apps, there have been many claims and tips provided to help reclaim a lost sense of smell.

One popular example involved eating a burnt orange to improve your smell. Others include using hydrogen peroxide to wash out your nose. It’s important to remember these claims are unsubstantiated and shouldn’t be conducted at home. 


If you or a loved one has experienced a loss of smell, contact your primary care physician or schedule an appointment with an ear, nose and throat doctor (otolaryngologist) at INTEGRIS Health.


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