7/21/2026
A college classmate shared an article with me yesterday about olfactory training, a rehabilitation method for people who have lost or impaired their sense of smell.
The original olfactory training protocol, developed by Thomas Hummel, uses four distinct scents—rose, lemon, eucalyptus, and clove—because each represents a different category of odor. The goal is to expose the olfactory system to a diverse range of chemical stimuli rather than repeatedly smelling similar scents.
Among these four, eucalyptus and clove have an additional feature. Besides stimulating the olfactory system, they also activate the trigeminal nerve, which detects sensations such as cooling, warmth, and mild irritation rather than smell itself.
One remarkable characteristic of the olfactory system is its ability to regenerate. Unlike most neurons in the central nervous system, olfactory receptor neurons are continuously replaced throughout life. This unique capacity is one reason smell rehabilitation is possible.
The most fascinating aspect of olfactory training, however, is the emphasis on conscious recall. Patients are encouraged not merely to smell a lemon, but to actively imagine it—to picture its bright yellow color, remember its fresh citrus aroma, and even recall the sensation of biting into it.
Modern neuroscience suggests that smell is much more than the simple detection of odor molecules. It is a complex cognitive process involving memory, emotion, expectation, previous experience, and focused attention.
When you smell a cup of coffee, for example, your brain is not just recognizing airborne chemicals. It is simultaneously retrieving memories, emotions, and associations built over a lifetime.
This emphasis on active attention, rather than passive smelling, fits well with what we know about the brain.
Whether learning a new language, recovering from a stroke, practicing the piano, or rehabilitating the sense of smell, focused and repeated practice is generally far more effective than passive exposure.
That is why many smell specialists encourage patients to do more than simply sniff an odor:
"Don't just smell it. Think about it. Imagine it vividly. Recall the memories it evokes. Pay attention to every faint sensation you experience."
This advice reflects one of the brain's most remarkable abilities—neuroplasticity, its capacity to reorganize and strengthen neural connections through repeated, purposeful practice. Although researchers are still investigating exactly how olfactory training works, the underlying principle is well supported.
What attracted me to this topic is not the treatment of smell loss but the broader insight that active mental engagement can help the brain heal and sharp.
This also makes me wonder whether olfactory training might benefit older adults in ways beyond restoring smell. Because the brain links odors so closely with memory and emotion, perhaps repeatedly recalling familiar scents helps exercise neural pathways associated with the hippocampus. Whether future research confirms this remains to be seen, but it is certainly an intriguing possibility.
So, sniff a fruit, focus your attention, imagine, and activate your hippocampus!
