Tip/Thought of the Day

Does Olfactory Training Restore the Ability to Smell?

Olfactory therapy, often referred to as smell training, has been a hot topic in light of the often lingering effect of Covid-19. The loss of smell was one of the most commonly reported symptoms of Covid-19. Research shows that roughly 90 percent of people experienced an improvement in their smell within one to four weeks and 95 percent of people recover by six months. But for others, the impact can last well beyond six months.

Loss of smell is tied to a variety of causes, including head trauma, chronic rhinosinusitis, and infections of the upper respiratory tract. While not yet completely understood, the loss of smell can also be an early warning sign of neurodegenerative diseases like dementia, Alzheimer‘s, and Parkinson’s disease. Other medical conditions can damage the nerves that lead to the smell center of your brain, as does Covid-19.

Smell impacts a wide range of functions- feeding habits, memory, stress, weight and how our body metabolizes food, pain levels, as well as other physiological functions such as sleep. Losing our sense of smell can consequently wreak havoc on our lives. Studies have linked loss of smell (and taste) to mental health decline as people lose the connection that arouses memories, adds another sensory layer to everything we experience and also keeps us safe (e.g. the ability to smell smoke or a gas leak). This is where smell therapy comes in.

What is smell therapy?

Smell retraining therapy (SRT) was originally developed in 2009 by Dr. Thomas Hummel at the University of Dresden. Sources share that smell training is a non-pharmacological and non-surgical treatment option for patients with olfactory dysfunction. Smell training is actively sniffing the same four scents every day, spending around 20 seconds on each scent.

Proponents of the treatment liken it to physical therapy for the olfactory bulb. Meant to restore and repair function, treatment focuses on reestablishing brain connectivity of pathways via memories and experiences tied to scent.

Each session follows these general guidelines:

  • Sniff each of the four scent for 10 to 20 seconds twice a day
  • While sniffing, concentrate on memories evoked by that smell, focus on the entirety of the experience around that memory- the setting, who was there, the weather, etc.
  • After each scent, take a few breaths and then move on to the next fragrance.
  • Continue the daily routine (twice daily) for up to 24 weeks.

There aren’t any specific four scents that must be used, but research has shown the most promise with the following four categories and scents:

  • Fruity (lemon)
  • Spicy (clove)
  • Floral (rose)
  • Resinous (woody, plant scents like eucalyptus)

Does it work?

While there isn’t yet an approved treatment for loss of smell (Covid-related or otherwise), smell training has become a recommended treatment by the American Academy of Otolaryngology–Head and Neck Surgery and has been supported by the chief medical officer of the Centers for Disease Control and Prevention. Researchers concede that while therapy shows promising results in some subjects, additional research is needed to:

  • Establish whether the origins of the smell disorder impact therapy results
  • More thoroughly understand outcomes
  • Determine the most effective duration of therapy (current studies show that this varied greatly)

However, the method has gained support as there aren’t any negative side effects to smell training. Smell training is something anybody can do in the comfort of their own homes, but research has shown that partnering with an Ear, Nose, and Throat provider may improve outcomes. A study conducted by researchers at Stanford University showed that olfactory therapy worked better when paired with sinus rinses that included steroids.


While smell therapy lasts for an extended period of time, it is simple and without any side effects. With no downside, smell therapy may be worth the effort if in the long run, it provides any advancement in repairing smell function and the consequent physiological and mental improvements.



-https://www.ncbi.nlm.nih.gov/books/NBK567741/

-https://news.bloomberglaw.com/health-law-and-business/cdc-touts-smell-training-after-covid-19-but-it-might-not-work

-https://www.frontiersin.org/articles/10.3389/fpubh.2021.666442/full

-https://pubmed.ncbi.nlm.nih.gov/26624966/

-https://pubmed.ncbi.nlm.nih.gov/28040824/

-https://pubmed.ncbi.nlm.nih.gov/25270839/

-https://pubmed.ncbi.nlm.nih.gov/33544097/

-https://medconnection.ucsfhealth.org/news/olfactory-loss-from-covid-19-infection-cause-and-treatments-studied-at-ucsf

-https://www.enthealth.org/be_ent_smart/smell-retraining-therapy/

-https://www.webmd.com/brain/ss/slideshow-causes-of-loss-of-smell-and-taste

-https://pubmed.ncbi.nlm.nih.gov/29901865/

-https://www.mayoclinic.org/diseases-conditions/chronic-sinusitis/symptoms-causes/syc-20351661

-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3794443/

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