"Smell on Radio Waves": 5 Minutes of Contactless Stimulation Increases Sensitivity to Smells for a Week

Korean researchers have shown that contactless radiofrequency (RF) stimulation of the olfactory nerve can significantly increase sensitivity to smells in healthy people. Just 5 minutes at a frequency of 2.45 GHz improved the perception threshold (according to the Sniffin' Sticks test) from 9.73±2.45 to 15.88±0.25 points - an almost "perfect" result, and the effect lasted up to a week after a single procedure. Electrophysiologically, this was accompanied by an increase in the response of the olfactory bulb (electrobulbogram, EBG) in the 30-100 Hz band. The authors position the method as a potential basis for a new treatment for olfactory loss (including post-viral), as well as a tool for maintaining the "smell" of perfumers, sommeliers and tasters.

Background of the study

Loss or weakening of the sense of smell is a common and underestimated problem, exacerbated by COVID-19 and an aging population. Not only does taste and pleasure from food suffer, but safety (recognition of smoke, gas, spoiled food) decreases, and mood and social well-being deteriorate. In practice, the main approach remains “olfactory training” - inhalation of standard aromas for many weeks. This method is relatively safe and accessible, but the effect in many patients is moderate and unpredictable, and it does not guarantee “fundamental” restoration of neural activity.

This is why non-invasive neuromodulation of the olfactory pathway is receiving more and more attention. It is difficult to directly “reach” the olfactory nerve: it lies deep, passes through the cribriform plate, and surface currents (tDCS/tACS) are strongly dissipated in the skin and bone. Radiofrequency (RF) fields are another physical channel: due to their wavelength, they penetrate tissue and bone better and are able to induce currents and change the excitability of neurons without contact with the skin and without implants. Plus, this is a controlled “dose” of stimulation: the frequency, power, duration and geometry of the antenna are set by the device, and safety is assessed through SAR and heating control.

In order for such approaches to move towards the clinic, objective markers of target structure involvement and validated behavioral tests are needed. For olfaction, these are, on the one hand, psychophysical methods like Sniffin' Sticks (threshold, discrimination, odor identification), and on the other, electrobulbogram (EBG), a non-invasive recording of the olfactory bulb activity from the forehead skin. The combination of "threshold test + EBG" allows us to distinguish real neural activation from the expectation effect and to estimate the duration of stimulation. Strict sham protocols (fictitious stimulation) and blind procedures are especially important.

The next step is to transfer experiments on healthy people to patients with post-viral, traumatic or age-related hypo/anosmia, optimize the modes (power, duration, frequency), evaluate the long-term effectiveness and safety during course use. Engineering will have to take into account the anatomical variability of the sinuses and frontal bone, miniaturization and convenience of home use. If the results are confirmed in multicenter RCTs, contactless RF stimulation can become a new class of olfactory rehabilitation - an independent tool or an addition to smell training - and at the same time a useful "professional add-on" for perfumers, sommeliers and tasters.

Why is this necessary?

Olfactory dysfunction, from hyposmia to anosmia, has increased in frequency due to COVID-19 and an aging population, significantly reducing quality of life: taste, safety (smoke/gas), and emotional well-being suffer. Today, “smell training” (inhaling standard aromas) is the most common approach, but it provides only modest and inconsistent benefits. The idea of directly activating olfactory pathways without implants and electrodes on the skin is attractive: RF waves penetrate tissue and bone better than surface electrical currents (tDCS/tACS), and allow for gentle modulation of the excitability of target neurons.

How it was done

A single-center, randomized, sham-controlled study included 28 healthy subjects (KVSS-II, the Korean version of Sniffin' Sticks). A patch antenna (5x5 cm) was fixed to a forehead patch 10 cm from the bridge of the nose; a continuous 2.45 GHz signal with a power of 5-20 W was delivered for 1, 5, or 10 minutes. Safety was verified by SAR modeling on a 3D head and forehead skin thermography: no overheating was observed for 5 minutes at 15 W. The effect on olfactory circuits was confirmed by EBG (eyebrow electrodes) before and after stimulation.

What we found (briefly and in numbers)

• Threshold for n-butanol: 9.73±2.45 at baseline → 12.30±2.55 after 1 minute of RF; → 15.83-15.88 after 5-10 minutes (10-20 W). The difference is highly significant. The effect lasted up to 7 days, and disappeared by the 10th day.
• Electrophysiology: The olfactory bulb response power at 30-100 Hz increased by an average of ≈29% (p≈0.0005); the spectrogram showed a consistent increase during stimulation.
• Natural odors: grape, banana, apple - improvement in threshold after RF for all tested odors (p<0.0001).
• Sham control: in an additional experiment of “dummy” stimulation (described in the supplementary materials), no increase was observed, which reduces the likelihood of a pure placebo effect.

How it can work

The authors assume that the RF field is capable of inducing currents and increasing the excitability of neurons in the olfactory nerve/bulb area, passing through the frontal bone. By selecting the frequency, power, and antenna geometry, it is possible to achieve local effects with a low thermal effect (SAR within the permissible limits). Unlike "chemical" aroma training, the RF approach does not require inhalation of substances, does not cause odor fatigue, and provides a repeatable dose of stimulation.

What does this mean in practice (carefully for now)

This is not about “superpowers,” but about a candidate for a new physiotherapy. If the results are reproduced in patients with post-viral anosmia/hyposmia, trauma, or neurodegenerative background, a contactless way to amplify the signal in the olfactory system will appear. For olfactory professionals, this is a potential working tool for maintaining sensitivity. But it is still a long way to a routine clinic: multicenter RCTs, protocol optimization, and remote safety monitoring are ahead.

Important design details

• Smell testing: Validated Sniffin' Sticks (threshold portion), the standard in clinical and scientific olfactory work, were used.
• Response recording: electrobulbogram (EBG) - non-invasive recording of olfactory bulb activity; the method is rapidly advancing but requires strict methodological settings.
• RF dosage: the effect was “near maximal” at 5 min/15-20 W; there were no statistically significant differences between 15 and 20 W - an important benchmark for future optimization.

Limits of Possibilities and Questions for Future Work

• Generalization: study on healthy individuals. Samples with hyposmia/anosmia (postviral, age-related, traumatic) and long-term observation are needed.
• Mechanism: Neural activation contribution vs. vascular/thermal components; detailed SAR mapping in real sinus/cribriform plate anatomy.
• Blind protocols: hard sham with simulated device heat/noise to minimize guessing.
• Head-to-head comparison: versus odor training, taVNS, focused ultrasound modulation (where applicable).
• Dose-time curves: what is better - rare "boosts" once a week or short series daily; is there tolerance/plasticity with course use?

Who could potentially benefit from this (if everything is confirmed)

• People with post-viral (including post-COVID) hyposmia/anosmia.
• For patients with age-related loss of sense of smell (safety in the elderly is a separate issue).
• For scent professionals: perfumers, sommeliers, coffee/tea tasters - as a “supportive” procedure before testing.
• For patients after TBI/surgeries in the area of the nose and base of the skull - as part of rehabilitation.

The advantages of the method - and what distinguishes it from "smell training"

• No contact or chemicals: no aromatic substances or risk of irritation/allergy; no need for electrodes on the skin.
• Dosability and repeatability: the field parameters are set by the hardware and do not depend on the “inhalation intensity”.
• Speed: 5 minutes - noticeable effect lasting for days, which promises convenient protocols.

Conclusion

The work demonstrates the fundamental possibility of enhancing sensitivity to smells in humans by contactless RF stimulation of the olfactory system: a short session gives a strong and week-long effect, confirmed both behaviorally (threshold) and electrophysiologically (EBG). Now it's time for clinical trials in patients and fine-tuning the regime - from power and time to the frequency of "boosts". If the effectiveness and safety are confirmed, we will have a new class of neuromodulation for olfactory senses - convenient, scalable and compatible with everyday rehabilitation.

Source: Bok J. et al. Non-contact radiofrequency stimulation to the olfactory nerve of human subjects. APL Bioengineering 9:036112 (2025). https://doi.org/10.1063/5.0275613