Phantosmia is the perception of a smell that has no external source, and it became one of the more unsettling lingering symptoms reported by people recovering from COVID-19. In a large survey of people with COVID-related smell problems, roughly one in three experienced phantom smells, with the frequency climbing steeply during the first two months after the initial loss of smell before leveling off. The condition often catches people off guard because it can appear weeks or months after the acute infection has resolved, and the smells themselves tend to be deeply unpleasant. Understanding why this happens requires looking at what the virus does to the delicate tissue inside the nose and how the brain responds when that tissue tries to repair itself.
What Phantom Smells Actually Smell Like
People dealing with post-COVID phantosmia overwhelmingly report foul odors rather than pleasant ones. In a study of patients during the Omicron wave in China, the most frequently described phantom smells were smoky, burnt, and rotten, and participants rated the pleasantness of their phantom smells quite low, averaging about 27 on a 100-point scale.1Heliyon. Smell, taste and chemesthesis disorders in patients with the SARS-CoV-2 during Omicron variant pandemic in China Broader data from across multiple pandemic waves confirms similar patterns: phantom smells of cigarette smoke, rotten or putrid odors, and burnt rubber were consistently the most common complaints.2Journal of Allergy and Clinical Immunology. Clinical characteristics of chronic COVID-19 chemosensory dysfunction across pandemic waves
These are not fleeting whiffs. Some people detect phantom smells constantly throughout the day, while others experience them in waves triggered by certain environments like kitchens, bathrooms, or crowded spaces. The smells can be strong enough to interfere with eating, since the brain struggles to separate real food odors from the phantom overlay of smoke or rot. For many people, the weirdness of smelling something nobody else can detect adds a layer of anxiety on top of the physical discomfort.
How Common This Is and When It Develops
Phantosmia is not a rare curiosity. Among people who developed smell disorders after COVID, the prevalence was about 37% in a large dataset of nearly 4,700 participants.3PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in That same study found something counterintuitive about the timing: phantom smells were not usually the first symptom to appear. Instead, the frequency of phantosmia increased sharply during the first eight weeks after smell loss began, then reached a plateau.3PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in In a separate case series, patients presented with phantom smells an average of about 34 days after their initial positive test.4PubMed Central. Phantosmia with COVID-19 Related Olfactory Dysfunction: Report of Nine Case
This delayed onset puzzles many patients who assumed the worst was behind them. The explanation, as we’ll see, lies in the biology of how nasal tissue repairs itself after viral damage. The phantom smells are not a sign that the infection is getting worse; they are more likely a byproduct of the nervous system’s attempt to rebuild.
Phantosmia was significantly more common among people infected during the first two waves of the pandemic. Still, around 30 to 40 percent of people infected in later waves reported phantom smells as well, so the phenomenon did not vanish with newer variants.2Journal of Allergy and Clinical Immunology. Clinical characteristics of chronic COVID-19 chemosensory dysfunction across pandemic waves
What the Virus Does Inside the Nose
The inside of your nose is lined with a specialized patch of tissue called the olfactory mucosa, where smell-detecting nerve cells are bundled alongside support cells. When researchers examined this tissue from COVID patients, they found that SARS-CoV-2 primarily infects the support cells, known as sustentacular cells, rather than the smell-detecting neurons themselves.5Cell. SARS-CoV-2 Infection of the Human Olfactory Mucosa and Olfactory Bulb This has been confirmed in both human autopsy tissue and animal models.6PubMed Central. SARS-CoV-2 infection of sustentacular cells disrupts olfactory signaling pathways
Sustentacular cells do not detect smells themselves, but they are essential to the neurons that do. They maintain the chemical environment the neurons need to function, help clear waste, and provide structural scaffolding. When these support cells are destroyed by the virus, the neurons lose their operating environment and stop signaling properly, even though they were never directly infected. Think of it like pulling the power supply out of a computer: the processor is intact, but it cannot run.
This explains the initial loss of smell that many COVID patients experience. But it also sets the stage for phantosmia, because what happens next, during recovery, is where things go sideways.
Why Recovery Itself Generates False Smells
The olfactory system has a remarkable trait: it is one of the few parts of the nervous system that regularly regenerates throughout life. After the virus damages the support cells and the local environment collapses, new neurons begin growing to replace lost or damaged ones. But this regeneration does not always go smoothly.
When surgeons have excised olfactory tissue from patients with phantosmia (in non-COVID cases studied before the pandemic), the tissue typically shows a reduced number of neurons, a higher ratio of immature to mature neurons, and disordered growth of nerve fibers, sometimes including small tangles called intraepithelial neuromas.7JAMA Otolaryngology–Head & Neck Surgery. Long-term Follow-up of Surgically Treated Phantosmia In other words, the new wiring gets tangled. Immature neurons that haven’t fully calibrated to specific odors can fire spontaneously or misfire, sending smell signals to the brain even when no odor molecule is present.
The damage is not limited to the nose. In brain tissue from COVID patients, researchers found elevated levels of inflammatory molecules in the olfactory bulb, brainstem, and cerebrum compared to tissue from people who died of other causes.8PubMed. COVID-19 Induces Neuroinflammation and Suppresses Peroxisomes in the Brain This neuroinflammation can alter how the brain processes incoming smell signals, potentially amplifying garbled signals from regenerating neurons into a full phantom perception.
Brain imaging offers additional evidence that the central smell-processing network is disrupted. Using high-resolution MRI in people with persistent post-COVID smell problems, researchers found that connectivity was reduced between key smell-processing regions, particularly the insula and the orbitofrontal and entorhinal cortices, and between the thalamus and the insula. At the same time, connectivity was increased between certain other regions, and there was thinning of the left orbitofrontal cortex.9Scientific Reports. Functional and structural olfactory changes in post-COVID-19 patients detected by 7 Tesla MRI The picture that emerges is of a smell network that has been rewired in patches: some connections weakened, others compensatorily strengthened, in ways that could easily produce erroneous smell perceptions.
So phantosmia after COVID is likely a two-level problem. Peripheral damage in the nose leads to chaotic regrowth that generates scrambled signals, and inflammation or connectivity changes in the brain alter how those signals are interpreted. Neither level alone fully explains it; the combination does.
How Phantosmia Differs from Parosmia
People often confuse phantosmia with parosmia, and the two frequently occur together after COVID, but they are distinct problems. Phantosmia is smelling something that isn’t there at all. Parosmia is a distortion of a real smell: coffee that smells like sewage, or chicken soup that smells burnt. In parosmia, there is always an external trigger; remove the trigger and the bad smell goes away. Phantosmia has no trigger. The phantom smell can appear while you’re sitting in a clean, odorless room.
Research on post-COVID smell disorders found that parosmia and phantosmia were both more common in COVID patients than in people with smell loss from other respiratory infections, and both had a greater negative impact on quality of life.10PubMed Central. Long-Term COVID-19 Smell and Taste Disorders Differ Significantly from Other Post-Infectious Cases The treatment picture also differs. Parosmia often improves as olfactory training helps recalibrate the brain’s response to real odors. Phantosmia is harder to address because there is no external stimulus to retrain against, so management tends to focus on identifying the underlying cause and providing symptom relief.11Current Allergy and Asthma Reports. Parosmia and Phantosmia: Managing Quality Disorders
That said, many COVID patients experience both simultaneously, and the two conditions share the same root cause of disordered neural regeneration. It is common for parosmia to develop first, with phantosmia following weeks later, though the reverse pattern also occurs.
Who Is More Likely to Develop Post-COVID Smell Problems
Not everyone who catches COVID loses their sense of smell, and not everyone who loses it develops phantosmia. Some risk factors for developing olfactory dysfunction after COVID have been identified. A large case-control study of over 4,200 patients found that younger people, women, and non-Asian patients were more likely to experience smell problems. Having seasonal allergies and being hospitalized for COVID both increased the odds.12The Permanente Journal. Unmasking Risk Factors for Post-COVID-19 Olfactory Dysfunction Resulting From Early Stages of the Pandemic: A Case-Control Study of Lost and Lingering Smells
The sex difference is worth noting because it runs counter to most other COVID outcomes, where men tend to fare worse. Women appear more vulnerable specifically to the olfactory complications, possibly due to hormonal influences on the olfactory epithelium or differences in immune response at the nasal mucosa. The age finding is also somewhat counterintuitive: younger people, who generally recover from acute COVID more quickly, seem more prone to developing these lingering qualitative smell disorders.
Pandemic wave also matters. People infected in the first two waves (typically the original and Alpha strains) had higher rates of phantosmia, with phantom smells being the most common chronic complaint at 59% among those reporting lingering symptoms.2Journal of Allergy and Clinical Immunology. Clinical characteristics of chronic COVID-19 chemosensory dysfunction across pandemic waves Later variants still caused phantosmia, but less frequently.
How Long It Lasts and Whether It Goes Away
This is the question most people with phantosmia want answered, and the news is mixed. A two-year follow-up study of people who lost their sense of smell after COVID found that about 38% reported complete recovery, roughly half reported partial recovery (which ranged from mild residual complaints to severe ongoing phantosmia or distorted smell), and about 10% reported no improvement at all.13PubMed Central. Recovery from Covid-19 smell loss: Two-years of follow up
Among people with chronic smell dysfunction, the average symptom duration was about two years. Seventy percent of those who contracted COVID in 2020 still reported ongoing dysfunction when surveyed. One specific finding stood out: people whose phantom smells took the form of cigarette smoke were more likely to have persistent symptoms.14PubMed Central. Determinants of persistence and recovery of chronic coronavirus disease 2019 chemosensory dysfunction Why cigarette smoke phantosmia would predict worse outcomes is not entirely clear, though it may reflect a deeper or more widespread pattern of neural miswiring.
One research group found that the presence of phantosmia early after COVID may itself be a predictor of longer-term measurable olfactory dysfunction, suggesting it is a marker of more significant underlying damage rather than a trivial side effect.15PubMed Central. Phantosmia May Predict Long-Term Measurable Olfactory Dysfunction After COVID-19 Many patients also described their recovery as undulating: improvement followed by setbacks, with good weeks and bad weeks rather than a steady linear return to normal.14PubMed Central. Determinants of persistence and recovery of chronic coronavirus disease 2019 chemosensory dysfunction
Treatment Options and What the Evidence Shows
There is no medication specifically approved for phantosmia, and the treatment landscape remains frustratingly thin. The most commonly studied intervention is olfactory training, which involves deliberately sniffing a set of distinct scents (often essential oils like rose, eucalyptus, lemon, and clove) for about 20 seconds each, twice a day, over several months. The idea is to stimulate the regenerating neurons with strong, distinct odor signals, encouraging proper reconnection.
A multicenter randomized trial comparing intensive olfactory training (using a broader range of scents rotated frequently) with standard training in post-COVID patients found that both groups showed meaningful improvement over time. However, the intensive version did not outperform the standard protocol.16PubMed Central. Intensive Olfactory Training in Post-COVID-19 Patients: A Multicenter Randomized Clinical Trial This suggests that the act of training itself helps, but adding complexity does not add much benefit. The mechanisms behind the training appear to work on multiple levels: stimulating new cell growth and receptor activity at the nasal lining, and prompting cortical changes and connectivity shifts in the brain.17PubMed Central. Olfactory training with essential oils for patients with post-COVID-19 smell dysfunction: A case series
Some clinicians have tried combining olfactory training with other interventions. A case series of eleven post-COVID phantosmia patients treated with a combination of olfactory training, nasal irrigation with a corticosteroid, and a ten-day course of oral steroids reported self-perceived improvement, though the study lacked a control group and was too small to draw strong conclusions.18Rhinology Online. Characterization, treatment modalities, and self-perceived improvement of post-COVID-19 phantosmia: a case series of eleven patients The steroid component is aimed at reducing local inflammation, which may help if neuroinflammation is contributing to the phantom signals.
Patient surveys paint a sobering picture of the treatment gap. Only about 4% of people with qualitative smell disorders (phantosmia and parosmia) reported having received any successful treatment, and 58% said they had received no treatment at all. Olfactory training was the most commonly attempted self-management strategy.19Ear, Nose & Throat Journal. Qualitative Olfactory Disorders: Patient Experiences and Self-Management This gap reflects the reality that most clinicians have limited tools for this condition and many patients end up managing it on their own.
Phantosmia as Part of the Broader Long COVID Picture
Phantom smells don’t exist in isolation for many patients. In surveys of people with chronic post-COVID smell and taste dysfunction, nearly half also reported persistent fatigue, about a quarter had decreased exercise tolerance, and a notable fraction reported difficulty breathing.2Journal of Allergy and Clinical Immunology. Clinical characteristics of chronic COVID-19 chemosensory dysfunction across pandemic waves Phantom smells were the single most commonly written-in “other symptom” among people with chronic chemosensory dysfunction, reported by 59% of those who elaborated on their lingering problems.
The overlap between phantosmia and broader long COVID symptoms makes sense given what we know about the mechanisms. If the virus triggers neuroinflammation in the olfactory bulb, it is plausible that similar inflammatory processes affect other brain regions involved in fatigue, autonomic regulation, and cognition. The olfactory bulb sits right at the interface between the nasal cavity and the brain, making it a potential entry corridor for broader neurological disruption.
For patients, this means phantosmia can serve as a kind of canary in the coal mine. If phantom smells are persisting, it may be worth discussing other lingering symptoms with a doctor even if those symptoms seem unrelated. And for researchers, phantosmia provides a measurable, specific symptom that can help track the neurological dimensions of long COVID over time, something that vaguer complaints like “brain fog” do not offer as readily.
When to See a Doctor and What to Rule Out
Phantosmia is not unique to COVID. It can result from head injuries, other respiratory infections, sinus disease, certain medications, neurological conditions, and in rare cases, psychiatric disorders or brain tumors. If phantom smells appeared without a preceding COVID infection, or if they are accompanied by symptoms like seizures, severe headaches, or one-sided weakness, medical evaluation is important to exclude other causes.
Even in the post-COVID context, an evaluation can be useful. In one case series, phantosmia appeared alongside objective hyposmia (reduced ability to smell) in some patients, while others tested with normal olfactory function despite their phantom smells.4PubMed Central. Phantosmia with COVID-19 Related Olfactory Dysfunction: Report of Nine Case Formal smell testing with standardized instruments can help clarify whether the overall olfactory system is recovering or still significantly impaired, which in turn helps guide expectations and treatment decisions. If phantom smells are the only remaining complaint and objective testing shows normal function, that is actually a more encouraging sign than if phantosmia persists alongside severe measurable loss.
There is no imaging test or blood marker that diagnoses phantosmia directly. Diagnosis is based on your description of the symptom. But if symptoms are severe, persistent, or worsening after many months, referral to an otolaryngologist or a smell and taste clinic can open the door to structured olfactory training programs, consideration of anti-inflammatory treatments, and monitoring over time. The field is still evolving, and clinical trials are ongoing, so staying connected with a specialist gives you access to emerging options as they become available.