A foam plug and a nose clip: the low-tech hunt for a smell-loss treatment

For vision there are lenses and surgery. For hearing there are aids and cochlear implants. For smell, the sense COVID turned from a rare complaint into a common one, there is nothing on the shelf. A small otolaryngology lab at Ohio State is testing whether the absence can be engineered around.

Kai Zhao's team has spent the last two years building wearable nasal devices that do for smell what a hearing aid does for sound. "You're amplifying the smell signal instead of the sound," Zhao said in describing the approach. The mechanism is mechanical, not neural: only a fraction of inhaled air reaches the olfactory cleft at the top of the nasal passage, where receptors feed the olfactory bulb. Zhao's devices are designed to redirect more of that air toward the receptors, on the theory that more signal in means more perceived smell out.

Zhao's group has prototyped two formats. One is a foam plug inserted into the nose that helps open odor flow through the upper passages. The other is a clip modeled on the kind synchronized swimmers use to keep water out, which pinches the nasal valve to enhance narrowing and concentrate airflow toward the olfactory cleft. The team published first-prototype results in BMC Medicine in March 2025 and presented the latest iteration, a 3D-printed version of the device, at a conference in April 2026.

The devices target anosmia, the clinical term for loss of smell. Jeremy Klein, a 51-year-old pastor in Ohio, lost his sense of smell in May 2025 after a COVID infection and is one of the participants in Zhao's trial. Klein described reaching for sour cream and getting milk that had gone off three days earlier, and being unable to smell the gas burner when his wife asked whether he had left the stove on. He is one patient. The lab's results, so far, are preliminary.

The cost of the absence is not just culinary. A working nose is a safety system: people with anosmia are less likely to detect gas leaks, smoke, or spoiled food, and anosmia is associated with higher rates of depression. Vision has glasses and surgery; hearing has aids and cochlear implants; smell has had neither a pharmaceutical option nor a device. The Food and Drug Administration has approved no standard treatment for post-viral smell loss.

Three other research programs are working on the same problem. Researchers at Harvard used spatial transcriptomics, a method that maps gene activity across tissue, to chart more than 1,000 odor receptors in the mouse olfactory bulb, publishing the map in Cell on April 28, 2026. The work identified a horizontal-stripe spatial code for odors, showed retinoic acid acts as a chemical signal in the system, and tied specific receptors to social odor domains, basic biology any future smell-restore therapy will have to respect. A separate 2025 paper described a biological approach, using CRISPR-Cas13 to demethylate globose basal cells, the stem cells that regenerate the olfactory epithelium after viral damage, in post-viral olfactory loss. And a 2024 review in Sensors and Actuators B: Chemical catalogued olfactory implants, devices that electrically stimulate the olfactory system directly, with Thomas Hummel of the University of Dresden as a long-standing commentator on the bionic-nose approach.

Zhao's prototypes sit on the mechanical, signal-amplification end of that range. The open question is whether they help patients whose smell loss is conductive, caused by airflow problems a wearable can plausibly fix, or only patients whose loss is neural, in which case more air toward the olfactory cleft is not the rate-limiting step. The team's published data covers small cohorts and short follow-up, and the April 2026 results have not yet gone through peer review.

Zhao's team has said a larger follow-up trial is in the works. For now, the prototypes are a real device with a real mechanism, not a treatment.