Smelling cotton candy, burnt toast, or cigarette smoke when nothing around you could be producing that scent is a phenomenon called phantosmia, and it is far more common than most people realize. A large population-based study of older adults found that about one in twenty people reported experiencing phantom smells, with “smoky” or “burnt” being the most frequently described type. Sweet phantom odors like cotton candy, vanilla, or caramel are less commonly reported but absolutely part of the spectrum. The causes range from entirely harmless post-viral quirks to conditions that genuinely need medical attention, and the difference usually comes down to how persistent the phantom smell is, whether it arrives alongside other symptoms, and what else is going on in your body at the time.
What a Phantom Smell Actually Is
A phantom smell is the perception of an odor when no external source exists. Clinicians distinguish this from parosmia, which is a distorted perception of a real smell that is present. If you walk into a bakery and the bread smells like gasoline, that is parosmia. If you are sitting in a clean room with no food, no candles, and no one cooking, and you distinctly smell cotton candy, that is phantosmia. The smell can be pleasant, neutral, or foul, and it can last seconds or linger for hours or even days. Brain imaging research has shown that during phantom smell episodes, the same sensory-specific brain regions that activate when you actually smell something light up, often with even greater intensity than responses to real odors. Your brain is genuinely generating the experience of a smell, not just a vague impression of one.
How Common Phantom Smells Are
Most people assume phantom smells are rare or a sign that something is seriously wrong. In reality, a study of a population-based sample of older adults found a prevalence of about 5%, with women being more likely to report them than men. Interestingly, having a reduced sense of smell (hyposmia) did not correlate with phantom smell experiences in that study, meaning your nose can be working perfectly well and you can still have phantom odors. The study also identified a genetic link: carrying a particular variant of the BDNF gene and having a higher vascular risk burden were both associated with phantom smells. This suggests that the causes are not purely nasal but involve brain-level processes.
Among people who have had olfactory disorders after an infection like COVID-19, the prevalence is dramatically higher. A large survey of people with COVID-related smell problems found that roughly 37% reported phantom smells. Phantosmia prevalence increased sharply during the first two months after the onset of smell loss, then plateaued, with no clear decline even 15 months out. That plateau is worth noting: for a sizable group of people, phantom smells after a viral infection are not a brief blip. They can become a persistent companion.
Post-Viral Phantosmia and COVID
Before 2020, post-viral olfactory dysfunction was a well-recognized phenomenon, but COVID made it mainstream. The virus has a particular affinity for olfactory nerve cells, and the damage it causes can scramble how your brain processes smell signals during recovery. As olfactory neurons regenerate and attempt to rewire, they sometimes misfire, producing phantom perceptions. Sweet smells like cotton candy are plausible in this context because the regenerating neurons may activate reward-associated olfactory pathways in incomplete or skewed ways.
The COVID phantosmia data paints a specific timeline. In a study of nearly 5,000 participants with COVID-related olfactory dysfunction, the relationship between how long the disorder had lasted and the presence of phantom smells followed a curve: a strong rise in the first couple of months, then a leveling off. Some participants initially confused their phantosmia with parosmia, which makes sense since the two conditions can coexist. Among those whose descriptions were clearly phantom smells (odor without any source), the prevalence settled around 37%.
Seizures and the Olfactory Brain
One of the more concerning causes of phantom smells is temporal lobe epilepsy. The temporal lobe sits close to the brain’s olfactory processing centers, and when seizure activity sparks there, it can produce vivid olfactory hallucinations called olfactory auras. These are brief, involuntary, and often described as unpleasant, though pleasant phantom smells occur too. A study of epilepsy patients found olfactory auras in about 5.5% of those with temporal lobe seizures, and the phantom smells were usually accompanied by other aura symptoms like a rising feeling in the stomach, nausea, or a sudden wave of fear. In a broader review of patients with epileptic olfactory auras, the temporal lobe was identified as the seizure origin in over 80% of cases.
The reason this matters for someone casually smelling cotton candy: an olfactory aura from a seizure is typically brief (seconds to a couple of minutes), stereotyped (the same smell each time), and accompanied by those other telltale signs. If your phantom smell arrives in a sudden flash, always smells the same, and comes with odd feelings in your gut or a dreamlike detachment, that pattern points toward seizure activity and warrants medical evaluation. One case report describes a woman whose family noticed behavioral changes alongside her reports of smelling perfume and aftershave; her EEG turned out to be grossly abnormal, and she improved substantially once treated with an anti-seizure medication.
Brain Tumors as a Rare but Serious Cause
Phantosmia can, in rare instances, be the presenting symptom of a brain tumor. A case report describes a 70-year-old woman with no prior health concerns who developed phantom smells and an abnormal taste sensation. Imaging revealed a brain mass that was confirmed by biopsy to be a glioblastoma. The authors emphasized that phantosmia combined with taste distortion (dysgeusia) should raise clinical suspicion for seizure auras, and that diagnostic imaging is important to rule out structural causes like infections or tumors.
To be clear, this is not a common scenario. The vast majority of people who smell cotton candy do not have a brain tumor. But the case illustrates why persistent, new-onset phantosmia in someone over 50, especially when paired with taste changes, personality shifts, or headaches, should prompt a conversation with a doctor. The reassuring flip side is that brain imaging can rule this out definitively and quickly.
Neurodegenerative Diseases
Smell loss is one of the earliest symptoms of both Parkinson’s disease and Alzheimer’s disease, often appearing years before motor or cognitive symptoms. Phantom smells specifically are less studied in this context, but research suggests they may be underrecognized. A systematic review of phantosmia in Parkinson’s disease found that comprehensive data is still lacking, but the phenomenon clearly occurs. In Alzheimer’s disease, one study found that about 2% of patients experienced olfactory hallucinations at baseline, with that figure climbing to roughly 4% over follow-up.
Researchers have suggested that phantosmia and other smell distortions in degenerative diseases may be more common than the current awareness implies, not only in Parkinson’s and Alzheimer’s but in other conditions that involve smell loss. The challenge is that patients with cognitive decline may not report phantom smells or may not be asked about them. If an older adult with early cognitive changes also reports smelling things that are not there, it is worth mentioning to their neurologist.
Medications That Can Trigger Phantom Smells
Several common prescription medications are associated with phantom odor perception. A study of U.S. adults aged 60 and older found that people taking antidiabetic medications, cholesterol-lowering drugs (antihyperlipidemic agents), or proton pump inhibitors had roughly 74% to 88% greater odds of reporting phantom smells compared to those not taking these medications. That is a meaningful increase, and these are among the most widely prescribed drug classes for older adults.
The mechanisms behind drug-induced smell disturbances vary. Some medications alter the flow of calcium and other ions across nerve cell membranes. Others deplete zinc, which plays a role in how olfactory receptors function. Still others interfere with prostaglandin pathways or other signaling molecules that support normal smell processing. If phantom smells started around the same time you began a new medication, that timing is worth flagging to your prescriber. In many cases, adjusting the dose or switching to a different drug resolves the phantom odor entirely.
Anxiety and Psychiatric Connections
Phantom smells are not always neurological in origin. They can be a feature of psychiatric conditions, particularly anxiety disorders. A case report described a 66-year-old woman who experienced progressively worsening olfactory hallucinations for nearly four years before being diagnosed with generalized anxiety disorder. The phantom smells disappeared after she was treated with anti-anxiety medication. The authors noted that olfactory hallucinations can be the first and only symptom in a patient with an anxiety disorder, sometimes preceding the formal diagnosis by years.
This is an underappreciated connection. When most people think of anxiety symptoms, they think of racing thoughts, chest tightness, or insomnia, not phantom smells. But the olfactory system is deeply wired into the brain’s emotional circuitry, particularly the amygdala and the limbic system. Heightened arousal states can amplify or distort sensory processing, and in some individuals, the result is a genuine olfactory hallucination. If you notice that phantom smells tend to appear during periods of high stress or after poor sleep, anxiety-related phantosmia is worth exploring with your doctor.
When the Sweet Smell Is Real
Before assuming a sweet smell is a phantom, consider whether there might be an actual source. One medical scenario worth knowing about is diabetic ketoacidosis (DKA), a serious complication of poorly managed diabetes. When the body breaks down fat for energy instead of glucose, it produces ketone bodies, one of which is acetone. Acetone on the breath has a characteristically sweet or fruity odor. In DKA, this is not a phantom; it is a real chemical smell produced by your own body. In one military case report, a sailor’s fruity breath was actually detected by a breathalyzer because the acetone had been converted to isopropanol, a substance the device could register.
If you or someone around you smells something persistently sweet and the person in question has diabetes, this is not a quirky sensory glitch. It is a potential medical emergency. DKA requires urgent treatment. The distinction between a phantom sweet smell and a metabolic sweet smell is straightforward: phantosmia is perceived only by the person experiencing it, while a metabolic odor can be detected by others standing nearby.
Head Injuries and Trauma
Traumatic brain injury is another established cause of phantosmia. A case report documented a 28-year-old man who developed complete bilateral anosmia (total loss of smell) after a serious head injury that damaged olfaction-related brain structures. Despite having no functional smell input from his nose, he experienced phantom smells. The finding illustrates something remarkable about how the brain handles smell: even years after olfactory receptors go silent, the neural circuitry that generates the experience of smelling can still fire on its own, producing odor sensations without any conscious recall triggering them. It is essentially the olfactory equivalent of phantom limb pain, where the brain continues to produce sensations from a system that is no longer sending input.
Workplace Chemical Exposure
Chronic exposure to certain chemicals in occupational settings can damage the olfactory system and lead to smell disturbances. Epidemiological research has identified metal compounds involving cadmium, chromium, and nickel, along with formaldehyde, as chemicals whose workplace exposure is associated with olfactory dysfunction. While most occupational olfactory damage presents as reduced smell rather than phantom smells, disruption of normal olfactory processing can sometimes tip into phantosmia as damaged neurons misfire during partial recovery. If you work in manufacturing, welding, plating, or other environments with metal fume or chemical vapor exposure, and you start noticing phantom smells, the occupational exposure is worth investigating as a contributing factor.
When to See a Doctor
A single fleeting episode of smelling something sweet that is not there is almost never a reason to panic. Occasional phantom smells happen to healthy people and resolve on their own. The situations where medical evaluation becomes important include:
- Persistence: the phantom smell occurs daily or near-daily for weeks and is not fading.
- Accompaniments: the smell arrives alongside other neurological symptoms like a rising sensation in the stomach, sudden fear, confusion, déjà vu, or brief lapses in awareness.
- New medications: the phantom smell started within weeks of beginning a new prescription.
- Head injury history: you had a concussion or more serious brain injury in the past, even years ago.
- Cognitive changes: the phantom smell is occurring alongside memory problems, mood changes, or difficulty with daily tasks.
- Diabetes: others can also smell the sweet odor, which may indicate a metabolic issue rather than a phantom.
A doctor evaluating persistent phantosmia will typically start with a thorough history and nasal examination. Depending on the clinical picture, brain MRI or CT imaging may be ordered to rule out structural causes, and an EEG may be warranted if seizure activity is suspected.
Treatment Options
Treatment for phantosmia depends entirely on the underlying cause. When a treatable condition is identified, addressing it often resolves the phantom smells. Anti-seizure medications work for epilepsy-related cases. Anti-anxiety medications resolved the olfactory hallucinations in the anxiety disorder case described above. Adjusting or discontinuing offending medications can eliminate drug-induced phantosmia.
For persistent phantosmia without an identifiable systemic cause, the options are more limited but do exist. A systematic review of treatments for long-lasting phantosmia found that surgical excision of the olfactory mucosa (the smell-detecting tissue inside the nose) provided short-term improvement in the majority of patients who underwent it. Medical treatments that have shown some success include antipsychotic medications like haloperidol, anti-migraine drugs, anti-seizure medications such as topiramate and gabapentin, and even topical application of cocaine to the olfactory region, which temporarily blocks the misfiring neurons. One case report described a patient whose phantosmia was cured by antibiotic treatment of a bacterial infection in the nasal passage, highlighting that sometimes the cause is more straightforward than expected.
A retrospective review of five patients with refractory phantosmia found that haloperidol worked for two of them over a three-month trial. The remaining three, whose phantosmia did not respond to medication, were treated surgically with removal of the olfactory lining and cutting of the olfactory nerves, which cured them. These surgical options are reserved for severe, quality-of-life-affecting cases that have failed everything else.
Olfactory Training During Recovery
For people recovering from post-viral smell disorders, including both phantosmia and parosmia, olfactory training has emerged as one of the most accessible rehabilitation approaches. The basic protocol involves deliberately and repeatedly sniffing a set of distinct odors (often rose, lemon, eucalyptus, and clove) for short sessions each day. The idea is to encourage neuroplasticity, helping damaged olfactory pathways rewire correctly. A study of modified olfactory training for COVID-induced parosmia found significant improvement in both a treatment group and a control group over nine months, but the treatment group improved more, and extending the training from six to nine months produced additional benefit in reducing distorted-smell complaints and improving the ability to discriminate between odors.
Olfactory training is not a guaranteed fix for phantosmia specifically, and much of the formal research has focused on parosmia and hyposmia. Still, the underlying principle of encouraging olfactory nerve recovery through structured stimulation applies broadly. It is low-risk, costs almost nothing, and can be done at home. For someone whose phantom cotton-candy smell is a post-viral artifact, consistent olfactory training over several months is one of the more evidence-supported things to try while waiting for natural recovery to take its course.
Why Sweet Smells in Particular
People often wonder why their phantom smell is specifically sweet, like cotton candy, caramel, or vanilla, rather than something neutral. The honest answer is that researchers do not fully understand why particular phantom odors manifest. The most commonly reported phantom smell in the population-based study was smoky or burnt, not sweet, so cotton candy is not the default. But sweet and pleasant phantom smells do get reported regularly, and there are a few possible explanations. The olfactory bulb and cortex have complex, overlapping receptor patterns for different odor categories, and when neurons misfire, the resulting percept depends on which specific populations of cells are involved. Sweet and food-related odors may recruit reward-circuit pathways in the brain more easily, making them more salient when they do appear as phantoms. It is also possible that people are more likely to notice and report pleasant phantom smells precisely because they are unexpected and puzzling. A faint smoky smell might be dismissed as a neighbor’s fireplace. A sudden whiff of cotton candy in your living room at midnight is harder to explain away.