Smelling bacon, smoke, or something burning when nothing is there is a phenomenon called phantosmia, and it affects a surprisingly large number of people. Population-level surveys estimate that roughly 5 to 7 percent of adults over 40 experience phantom odors at some point, with women reporting them about twice as often as men.1JAMA Otolaryngology–Head & Neck Surgery. Factors Associated With Phantom Odor Perception Among US Adults The causes range from harmless post-viral nerve recovery to serious neurological conditions, which is why understanding what drives these ghost smells matters more than the smell itself.
What Phantosmia Actually Is
Phantosmia is the perception of a smell when no chemical source is present. Your nose and brain generate the sensation entirely on their own. This distinguishes it from parosmia, where a real odor is present but your brain misinterprets it, so coffee might smell like sewage or flowers might smell like chemicals.2PubMed Central. Parosmia and Phantosmia: Managing Quality Disorders The two conditions often overlap, but the core difference is simple: parosmia distorts something real, while phantosmia invents something from nothing.
Under normal conditions, smell works by odorant molecules binding to specialized receptors high up in the nasal cavity. Those receptors convert chemical information into electrical signals, which travel via the olfactory bulb to several brain regions for processing.3PubMed Central. Sense of Smell: Structural, Functional, Mechanistic Advancements and Challenges in Human Olfactory Research Phantosmia means something has gone wrong somewhere along this chain, either at the receptor end in the nose or deeper inside the brain. That distinction between a “nose problem” and a “brain problem” is the first thing clinicians try to sort out when someone complains of phantom smells.
What Most People Actually Smell
If you are smelling bacon, you are in good company, though the single most common phantom smell is something smoky or burnt. In one population-based study of older adults who reported phantom smells, nearly half described the odor as smoky or burning. Other reported smells included mold, metallic or chemical scents, perfume, flowers, cooked food, and rotting or dusty odors. About a quarter of people reported more than one type of phantom smell.4PubMed Central. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults Bacon, toast, and smoke all cluster in that “burnt” category, which is why a phantom whiff of bacon is one of the more frequently Googled versions of the experience.
Pleasant phantom smells, like flowers or fresh bread, do happen, but unpleasant ones dominate the research literature and the doctor’s office. People tend not to seek medical attention for a phantom smell they enjoy. The ones that prompt concern are the persistent burnt, chemical, or foul smells that interfere with eating, socializing, or just getting through the day.
How Common Phantom Smells Are
Phantosmia is not rare. A nationally representative U.S. survey found that about 6.5 percent of adults aged 40 and older reported experiencing phantom odors. Women had roughly double the prevalence at every age group, and the rates actually declined with age, meaning younger middle-aged adults were more likely to report them than the elderly.1JAMA Otolaryngology–Head & Neck Surgery. Factors Associated With Phantom Odor Perception Among US Adults A separate study focusing on older adults found a prevalence closer to 5 percent, and linked phantom smells to female sex, higher cardiovascular risk, and a specific genetic variant related to brain-derived neurotrophic factor.4PubMed Central. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults
Among people who already have some form of smell disorder, phantom smells are even more common. A large survey of over two thousand people with at least one olfactory problem found that about 11 percent experienced phantosmia alone, while another 16 percent had both phantosmia and parosmia.5PubMed Central. Prevalence and correlates of parosmia and phantosmia among smell disorders People whose smell disorders followed head trauma were particularly likely to develop phantom smells, whereas post-viral olfactory loss was more strongly tied to parosmia.
Post-Viral Causes, Including COVID-19
The COVID-19 pandemic put phantom smells in the spotlight. Many people who lost their sense of smell after infection found that, weeks or months later, phantom odors appeared during the recovery period. One study of COVID-19 patients with olfactory dysfunction found a phantosmia prevalence of 37 percent. Women were more affected, and phantosmia was particularly common among people whose smell loss came on gradually, lasted longer, or fluctuated rather than remaining total and permanent.6PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in
This pattern makes sense when you consider what happens after a virus damages the olfactory nerve cells in the nose. Those cells can regenerate, but the regrowth is imperfect. New nerve fibers sometimes wire back to the wrong receptors in the olfactory bulb, and the brain receives jumbled signals it tries to make sense of. During this messy recovery period, the brain may generate phantom perceptions. A case series of post-COVID phantosmia patients, averaging around 29 years of age with no other health conditions, described the experience as having lasting effects on daily life. That study explored combinations of olfactory training, nasal rinses with budesonide, and oral steroids as potential treatments.7Rhinology Online. Characterization, treatment modalities, and self-perceived improvement of post-COVID-19 phantosmia
Other viruses can cause the same thing. Upper respiratory infections have long been recognized as a trigger for olfactory dysfunction, and the general mechanism of damaged-then-regenerating sensory neurons applies broadly, not just to SARS-CoV-2.
Peripheral Versus Central Origins
Clinicians divide phantosmia into two broad categories based on where the problem originates. Peripheral phantosmia arises from disruption of the olfactory lining in the nose and the sensory receptors themselves. Central phantosmia originates deeper, from abnormal processing and interpretation within the brain.8PubMed. Phantosmia This distinction is clinically useful because the causes, severity, and treatment options differ substantially depending on which side of the divide you fall on.
One diagnostic clue is whether the phantom smell affects one nostril or both. Peripheral causes tend to produce phantom smells that are stronger on one side, or that can be temporarily blocked by numbing the olfactory tissue in the affected nostril. Central causes typically produce smells that persist no matter what you do to the nose. In experiments where a local anesthetic was applied to the olfactory region, it caused a temporary reduction in smell perception, peaking at about a 35 percent decrease within 15 minutes.9PubMed Central. Effect of Lidocaine on Olfactory Perception in Humans When similar topical anesthetics were tried on phantosmia patients specifically using cocaine solution, the results were less encouraging for long-term relief. Researchers observed no lasting benefit, and when cocaine was applied to only one nostril, smell ability actually decreased on the opposite side too, suggesting the brain’s central processing was involved even in cases that seemed peripheral at first.10PubMed. Olfactory cocainization is not an effective long-term treatment for phantosmia
Epilepsy and Temporal Lobe Seizures
A sudden, brief phantom smell that happens repeatedly in the same pattern, often followed by a strange feeling of déjà vu or a wave of confusion, can be a seizure aura. Temporal lobe epilepsy is the neurological condition most classically associated with olfactory hallucinations. In a study of patients with temporal lobe epilepsy, about 5.5 percent experienced olfactory auras, and brain imaging showed structural involvement of the mesial temporal structures, with the amygdala appearing to play a key role in generating these phantom smells.11PubMed. Olfactory auras in patients with temporal lobe epilepsy
A separate study looking at a condition called transient epileptic amnesia found olfactory hallucinations in over half of participants. These were typically described as a “funny smell” that appeared just before or during memory-loss episodes, though in some cases the phantom smell also arose at other times unconnected to the amnestic attacks.12PubMed Central. On the nose: olfactory disturbances in Transient Epileptic Amnesia If your phantom smell is brief, stereotyped (the same smell every time), and accompanied by any altered state of consciousness, seeing a neurologist promptly is worthwhile.
Migraine Auras
Migraine is better known for visual auras like zigzag lines or blind spots, but olfactory auras exist too. Some migraine sufferers smell something distinctive, sometimes burnt or chemical, in the hours or minutes before a headache strikes. Case reports describe patients experiencing phantom smells as a reliable warning sign of an approaching migraine, as well as patients who develop longstanding phantom smells connected to their migraine disease.13PubMed Central. Various presentations of the olfactory hallucination in two patients with migraine disease Olfactory auras in migraine are thought to arise from the same cortical spreading wave of altered brain activity that generates visual and sensory auras, just extending to smell-processing regions.
If you notice a consistent phantom smell before your headaches, mention it to your doctor. It can help refine the diagnosis and inform treatment choices, particularly because some migraine preventive medications can also reduce the frequency of aura symptoms.
Brain Tumors and Structural Lesions
This is the possibility that worries most people, and while it is genuinely rare, it is real. Phantom smells have been documented as the first presenting symptom of brain tumors, including aggressive types like glioblastoma. In one reported case, a previously healthy 70-year-old woman developed phantom smells and distorted taste, which turned out to be caused by a brain tumor confirmed on biopsy.14PubMed Central. Phantosmia and dysgeusia as the first presentation of glioblastoma In another, a breast cancer patient developed sudden phantom smells that led to the discovery of a brain metastasis in the right orbitofrontal cortex, a region directly involved in processing smell.15PubMed Central. Acute phantosmia as the first manifestaton of brain metastases in a patient with breast cancer
These cases are reported precisely because they are unusual, and the vast majority of phantom smells are not caused by tumors. Still, they illustrate why persistent, unexplained phantosmia, especially when it is new, worsening, or accompanied by headaches, seizures, personality changes, or any focal neurological symptoms, deserves brain imaging to rule out structural causes.
Medications That Can Trigger Phantom Smells
Certain prescription drugs are associated with a higher likelihood of phantom odor perception, particularly in older adults. A study using nationally representative U.S. health data found that among adults 60 and older, taking diabetes medications, cholesterol-lowering drugs, or proton pump inhibitors (the acid-reflux pills) was linked to roughly 74 to 88 percent greater odds of reporting phantom smells compared to people not on those medications.16PubMed Central. Prescription Medication Use and Phantom Odor Perception Among US Adults That does not mean the drugs directly cause phantosmia in every case. The conditions being treated, like diabetes and vascular disease, themselves affect the olfactory system. But the association is strong enough to be worth noting if you started smelling something odd around the time you began a new medication.
Beyond prescription drugs, environmental exposures such as chronic chemical fumes, heavy metals, and certain industrial solvents are known to damage olfactory neurons and could theoretically set the stage for phantom smells during recovery or ongoing exposure. If your work environment involves heavy chemical exposure and you develop unexplained smells, that context is relevant information for your doctor.
Anxiety, Stress, and Psychiatric Connections
Phantom smells do not always trace back to something structural or infectious. Anxiety and stress have their own relationship with olfactory perception. Population-based research has found that self-reported anxiety symptoms and stressful life events are significantly associated with olfactory hallucinations.17PubMed. Olfactory hallucinations in a population-based sample And while olfactory hallucinations are well recognized in conditions like schizophrenia, they can also appear as the first and only symptom in someone with an anxiety disorder, a presentation that remains underrecognized clinically.18PubMed Central. First-episode olfactory hallucination in a patient with anxiety disorder
Anxiety appears to tune the olfactory system toward threat detection. Brain imaging research has shown that anxious individuals have heightened activity in the piriform cortex, the brain’s primary smell-processing area, in response to unpleasant odors. Their piriform cortex also shows stronger functional connections to the amygdala and hippocampus, brain regions tied to emotion and memory.19PubMed Central. Enhanced Olfactory Sensory Perception of Threat in Anxiety This hyper-responsiveness to negative smells could help explain why anxious people are more likely to perceive phantom odors, and why those phantom odors tend to be unpleasant rather than neutral or pleasant.
Broader olfactory disruptions are documented across several mental health conditions. Depression, bipolar disorder, and schizophrenia each involve specific alterations in how odors are identified and how their pleasantness or unpleasantness is perceived.20PubMed Central. Olfactory Dysfunction in Mental Illness This does not mean phantom smells indicate a psychiatric diagnosis, but if you are experiencing both phantom smells and significant mood or anxiety symptoms, the two may be connected and worth discussing together with a clinician.
When to See a Doctor
A fleeting phantom smell that happens once and never returns is almost certainly harmless. Many people experience brief olfactory glitches, especially when they are tired, congested, or recovering from a cold. The situations that warrant medical attention include phantom smells that are persistent or worsening over weeks, smells that follow a pattern suggestive of seizure activity, smells that started after head trauma, and phantom smells accompanied by other neurological changes like confusion, memory issues, or vision problems.
The diagnostic workup typically starts with a thorough history and nasal examination to look for sinus disease or infection. In one unusual case, phantosmia was cured entirely by antibiotic treatment of a bacterial infection in the nasal cavity, specifically a Pseudomonas stutzeri infection that had been present without other obvious symptoms.21PubMed Central. A case study of phantosmia cured by antibiotic treatment of an intranasal Pseudomonas stutzeri infection If the cause is not obvious from the nasal exam, brain imaging with MRI is often the next step, particularly to exclude tumors, lesions, or signs of temporal lobe pathology.
Treatment Options and Their Limits
Treatment depends entirely on the underlying cause. Post-viral phantosmia often resolves on its own as olfactory nerves finish regenerating, though the timeline can stretch from weeks to many months. Olfactory training, which involves deliberately sniffing a set of strong odors (like rose, eucalyptus, lemon, and clove) twice daily for several months, is the most widely recommended therapy for post-viral olfactory dysfunction, including phantom smells. Nasal rinses with corticosteroids and short courses of oral steroids have also been tried with varying results.
For peripheral phantosmia that does not respond to conservative measures, surgical excision of the olfactory lining has been described as effective in cases where the phantom smell had persisted for years.21PubMed Central. A case study of phantosmia cured by antibiotic treatment of an intranasal Pseudomonas stutzeri infection This is a drastic option that sacrifices any remaining sense of smell in the treated nostril, so it is reserved for people whose quality of life is severely impaired and who have exhausted other options. For seizure-related phantosmia, anticonvulsant medications address the root cause. For migraine-associated phantom smells, migraine preventive therapy is the approach. And for medication-associated phantom odors, switching drugs, when medically feasible, sometimes resolves the problem.
How Phantom Smells Affect Daily Life
People who have never experienced persistent phantom smells tend to underestimate how disruptive they can be. A large survey of a thousand patients with olfactory dysfunction found that many described the condition as genuinely debilitating. Beyond the practical annoyances, like not being able to enjoy meals or detect real dangers such as gas leaks, people reported social isolation and a loss of pleasure in everyday activities that researchers described as smell-loss-induced anhedonia.22PubMed Central. Hidden consequences of olfactory dysfunction: a patient report series When the smell you constantly perceive is something unpleasant, like burnt rubber or rotting food, the psychological toll compounds. Eating becomes aversive, social situations feel uncomfortable, and the constant uncertainty about whether the smell is real or not creates its own layer of anxiety.
The U.S. survey data also revealed a socioeconomic dimension: about two-thirds of people reporting phantom odors had household incomes below 300 percent of the poverty level, compared to less than half of those without phantom smells.1JAMA Otolaryngology–Head & Neck Surgery. Factors Associated With Phantom Odor Perception Among US Adults The reasons for this are not entirely clear, but likely involve greater exposure to environmental hazards, less access to medical care, higher rates of the chronic conditions associated with phantosmia, and possibly nutritional factors that affect olfactory nerve health. Whatever the explanation, it means phantom smells disproportionately burden people who already face barriers to getting help for them.