Smell Loss Affects Up to 22 Percent of People. Science Is Finally Paying Attention.

A Condition Dismissed for Decades

About 14 years ago, Chrissi Kelly lost her sense of smell after catching a virus during a trip to the Czech Republic. She saw her general practitioner. She saw an ear, nose and throat specialist. Both told her the same thing: learn to live with it.

"After about six months of complete loss, I was just climbing the walls, and I did not feel like myself anymore," Kelly told Ars Technica.

Her experience was not unusual. Researchers estimate that up to 22 percent of the population lives with some form of smell impairment, ranging from hyposmia (partial loss) to anosmia (complete loss). Others deal with phantosmia, where phantom smells appear from nowhere, or parosmia, where normal scents like coffee or shampoo register as something closer to feces or vomit. For years, clinicians largely shrugged at all of it.

Covid Forced the Issue

The pandemic broke that indifference. The World Health Organization has recorded 780 million reported Covid-19 cases since December 2019, with the true number substantially higher. Smell loss emerged as one of the virus's signature symptoms.

A 2023 survey published in the journal Laryngoscope found that 60 percent of individuals with Covid experienced smell loss. Most recovered. Some did not.

With millions of people losing the same sense simultaneously, the research community had a problem it could no longer ignore. Funding followed. So did papers.

The Science Behind Why Smell Matters

For most of medical history, smell was treated as the least important of the senses. In the 19th century, French brain researcher Paul Broca labeled olfaction "the bestial sense," arguing that humans had traded a sharp nose for higher intellect. That framing held sway for over a century and contributed to scientific neglect of the field.

Modern research has dismantled it.

Smell works through specialized receptors in the nasal cavity. Millions of olfactory neurons detect airborne molecules and send electrical signals through the olfactory bulbs, which build a sensory map in the brain for identifying, distinguishing, and remembering scents. The critical difference between smell and the other senses: those signals go directly to the amygdala, which governs emotion, and the hippocampus, which governs memory. No relay through the thalamus. A straight line.

That architecture explains why a particular smell can surface a 30-year-old memory with no warning. It also explains why smell loss hits people harder than most doctors predict.

"Humans are actually quite good at smelling," says Swedish psychologist Jonas Olofsson, author of The Forgotten Sense: The New Science of Smell and the Extraordinary Power of the Nose. Research confirms smell helps parents and children bond, warns people of environmental hazards, and anchors emotional memory in ways that other senses do not replicate.

The Brain Health Connection

The concern extends well beyond quality of life. Evidence is mounting that smell loss correlates with broader neurological decline. The olfactory system's direct connection to memory and emotion centers means impairment there may be an early signal of deterioration elsewhere in the brain. This line of inquiry has gained significant traction in dementia research, and Covid's mass anosmia cases have accelerated it by giving researchers an unprecedentedly large and documented patient population to study.

The Strongest Counterpoint

A reasonable objection to elevated alarm: most Covid-related smell loss resolved on its own, sometimes within weeks. The 2023 Laryngoscope survey found the majority of cases were temporary. Critics of over-medicalizing smell loss argue that for most people it is a transient symptom, not a chronic condition, and that research dollars are finite. Prioritizing smell disorders over more immediately life-threatening conditions is a legitimate resource allocation question.

This concern has validity for temporary cases. Yet it does not account for the significant minority of patients whose loss is permanent or long-term, the 22 percent population-level prevalence figure that predates Covid entirely, and the emerging evidence tying olfactory health to dementia risk. Temporary inconvenience for most does not negate a serious condition for millions.

What Hasn't Been Solved

For patients like Chrissi Kelly, acknowledgment from researchers is progress. Treatment, however, remains limited. Smell training — repeated, deliberate exposure to specific scents — has shown some benefit, but it is slow and does not work for everyone. There is no approved pharmaceutical intervention for post-viral anosmia as of July 2026.

The open question researchers have not yet answered: whether the olfactory damage caused by Covid follows the same biological pathway as smell loss from other viral triggers, or whether Covid created a distinct mechanism requiring its own targeted treatment. That distinction will determine whether the flood of post-Covid smell research translates into therapies that help the broader anosmia population, or only those whose loss was Covid-specific.