How Olfactory Training Can Improve Your Sense of Smell
Olfactory training, often referred to as “smell therapy,” has gained popularity not only for COVID-19 patients but also for those with various olfactory-related issues, including anosmia, hyposmia (reduced sense of smell), and parosmia (distorted sense of smell). Here’s how olfactory training works and why it’s so effective:
- Rebuilding Neural Pathways: Olfactory training involves regularly exposing yourself to a set of distinct scents. By doing so, you’re essentially exercising your olfactory system, helping to rebuild the neural pathways responsible for detecting and processing smells.
- Patience and Consistency: Olfactory training requires patience and consistency. It may take weeks or even months before noticeable improvements occur. However, many individuals report significant progress in regaining their sense of smell and the associated emotional benefits.
- Emotional Impact: Beyond the physical aspect of regaining smell, olfactory training can have a profound emotional impact. As individuals start to perceive scents again, they often experience a renewed sense of joy and connection to the world around them.
What Is Olfactory Training?
Olfactory training (OT) involves sniffing specific aromatics regularly in a structured way. Usually, it means sniffing 4 target essential oils – like lemon, rose, clove, and eucalyptus – twice daily for several months. You can choose any 4 essential oils or CO2 extracts in the essential oil palette. We recommend selecting 4 essential oils you have love or have a relationship with. The original 2009 study had participants sniff each odor intensely for 10 seconds with 10-second breaks in between. This was repeated to make a session of around 40 seconds, done twice a day.
But variations have been tested, too – like changing the aromas every few weeks, using more aromas per session, or making sessions longer. The key factor is that certain aromas are sniffed frequently over an extended time. This repetitive exposure stimulates and strengthens the olfactory system.
Who Benefits from Smell Training?
Olfactory Training (OT) was first developed as a treatment for people who lost their sense of smell from infections, injuries, or unknown causes. Studies show it can help up to 50-70% of these patients significantly improve their smell function, especially if done for at least 3-4 months. This recovery rate is much higher than the ~5-35% who tend to improve on their own without OT.
OT is now recommended as a first-line treatment for smell loss, including for COVID-19 patients struggling with long-term smell problems. Combining OT with steroid nasal sprays may enhance the effects.
Interestingly, smell training can also benefit those without smell disorders. Older adults who perform it tend to experience less decline in their smell ability over time. And young, healthy individuals who do more complex OT-like tasks show improvements in odor discrimination and identification. This suggests that repeatedly engaging your nose and olfactory brain areas strengthens those systems, just like physical exercise builds muscles and fitness.
How Does Smell Training Work?
Research shows OT actually changes both the structures and functions of olfactory pathways in the peripheral and central nervous systems.
In the nose, OT increases the number of electrical signals the olfactory nerves fire in response to odors. This indicates the detection of smells is enhanced. OT also boosts expression of olfactory receptors – the specialized proteins that bind to odor molecules.
Higher up, OT is associated with growth in the size of olfactory brain areas. The olfactory bulbs become enlarged, probably from increased neural activation. OT also thickens the cortex of brain regions that process smells and links them to memory and emotions.
Additionally, fMRI scans reveal that OT alters functional connectivity between olfactory areas and networks involved in sensory integration and cognition. This neural rewiring may support the improvements in smell skills.
The cellular and molecular changes from OT are not totally understood yet. But animal studies suggest it may stimulate neuroregeneration – the production of new olfactory sensory neurons from stem cells. OT also seems to up-regulate genes involved in neuronal survival and plasticity. Further research on these effects is needed.
Other Benefits of Smell Training
Aside from enhancing smell function, OT may provide broader cognitive benefits. Some studies have observed improvements in verbal skills, short-term memory, and processing speed in those who undergo OT. It seems repetitively using the olfactory system stimulates activity in allied brain networks that control attention, memory, and language. These changes may mitigate normal cognitive decline with aging.
There’s also tentative evidence OT could lessen depressive symptoms in those with mild depression. This makes sense given the links between olfaction, emotion, and mood regulation via limbic system structures like the amygdala. However, more research is required to determine exactly who may benefit in this regard.
Key Tips for Effective Smell Training
- Use 4 target aromas – such as eucalyptus, lemon, rose, and clove oils. Or any other 4 essential oils you love. Stick with the same aromas for at least 12 weeks before changing them up. Avoid strongly pleasant or unpleasant scents.
- Sniff each essential oil deeply and attentively for 10 seconds, taking 10-second breaks between essential oils. Repeat this sequence to make a session.
- Do sessions twice daily – morning and evening work well. But consistency matters more than timing.
- Continue OT for at least 12-24 weeks for best results. Be patient – improvement happens gradually.
- Keep track of your training with a log to stay motivated.
- OT kits are available, but you can DIY. Use authentic plant-derived essential oils or scented balms – about 10 drops per jar.
The Future of Smell Training
After 13 years of research, OT is now an established olfactory rehabilitation technique. However, questions remain about the optimal protocols and mechanisms. Controlled trials continue to refine OT methods and explore new applications. Emerging technologies even allow virtual OT through smartphone apps. As our knowledge expands, smell training promises to become an increasingly potent tool for boosting olfactory and cognitive health.
Pieniak, M., Oleszkiewicz, A., Avaro, V., Calegari, F., & Hummel, T. (2022). Olfactory training – Thirteen years of research reviewed. Neuroscience and Biobehavioral Reviews, 141, 104853. https://doi.org/10.1016/j.neubiorev.2022.104853