Smelling bleach when there is no bleach around is a phenomenon called phantosmia, and it happens when your brain generates a smell perception without any external source. Chemical and burnt odors are among the most commonly reported phantom smells, so a bleach-like sensation fits squarely within the pattern. The causes range from mundane sinus problems and lingering effects of a viral infection to, more rarely, neurological conditions that deserve medical attention.
What Phantosmia Is and How It Differs From Distorted Smell
Phantosmia is classified as a qualitative olfactory disorder, meaning the problem is not that you have lost your sense of smell but that the signals are scrambled. An international consensus statement on olfactory disorders defines phantosmia as the perception of an odor without an external stimulus, with common descriptors including “burned,” “chemical,” and “like cigarette smoke.”1PubMed Central. International consensus statement on allergy and rhinology: Olfaction That description tracks closely with what people who report smelling bleach are experiencing.
People sometimes confuse phantosmia with parosmia, but the two are distinct. Parosmia is the distortion of a real smell that is actually present: coffee might smell like sewage, or flowers might smell rotten. Phantosmia, by contrast, involves smelling something when there is nothing in the environment to smell at all.2PubMed Central. Parosmia and Phantosmia: Managing Quality Disorders Both can occur together, and both are distressing, but they point to somewhat different things going on in the olfactory system.
How Common Phantom Smells Are
Phantom smells are more widespread than most people realize. A nationally representative U.S. survey found that prevalence varied by age and sex, but the numbers were not trivial. Among women aged 40 to 59, roughly one in ten reported experiencing phantom odors. Among men, rates were lower, peaking around one in twenty in the 60-to-69 age range.3JAMA Otolaryngology–Head & Neck Surgery. Factors Associated With Phantom Odor Perception Among US Adults: Findings From the National Health and Nutrition Examination Survey That gender gap, with women consistently more affected, shows up across multiple studies and conditions.
A population-based study of older adults found an overall phantosmia prevalence of about 5%, with the most frequently reported type being smoky or burnt smells. Among those who had phantom smells, about a third had been experiencing them for more than a decade, while roughly one in six said they had dealt with it their entire life.4Oxford University Press. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults So for many people, phantom smells are a long-term companion rather than a brief episode.
The Post-Viral Connection, Especially COVID-19
If you started smelling bleach after a respiratory illness, a viral infection is the most likely explanation. COVID-19 put phantom smells on the map for millions of people. In a large study of more than 4,600 people with COVID-related smell disorders, about 37% reported phantom smells.5PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in That is a strikingly high rate, and the study found that phantosmia was more likely when smell loss was partial rather than total, when it came on gradually rather than suddenly, and when it fluctuated rather than stayed constant.
Women in that study were roughly 60% more likely to report phantom smells than men, and the probability of phantosmia increased the longer a person’s smell dysfunction lasted. The researchers modeled risk profiles and found that a woman with partial, fluctuating, long-lasting smell loss that set in gradually had over a 90% predicted probability of experiencing phantom smells, while a man with sudden, total, short-lived smell loss had only about a 15% probability.5PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in This pattern suggests that phantosmia emerges during recovery, as damaged olfactory neurons are regenerating and misfiring along the way. COVID is the virus that brought the most attention to this, but other respiratory viruses, including influenza and common-cold viruses, can produce the same aftermath.
Nasal and Sinus Infections
Sometimes phantom smells originate not from the brain but from something happening locally in the nose. Bacterial infections within the nasal cavity can produce odor-causing compounds right at the source, and the resulting smell may be perceived as constant and chemical. One documented case involved a patient whose phantosmia was caused by a bacterial infection inside the nose. That patient’s phantom smell resolved completely with antibiotic treatment, confirming it was a peripheral rather than central cause.6PubMed Central. A case study of phantosmia cured by antibiotic treatment of an intranasal Pseudomonas stutzeri infection
There is actually a useful clinical distinction here. A peripheral phantosmia, one originating in the nose or olfactory nerve endings, tends to be triggered by other smells but is not always present. It can often be localized to one side of the nose and may temporarily improve with simple interventions like nasal rinsing, crying, or taping the nostril closed on the affected side.6PubMed Central. A case study of phantosmia cured by antibiotic treatment of an intranasal Pseudomonas stutzeri infection If you notice that blocking one nostril makes the phantom bleach smell go away, that is a meaningful clue that the problem lives in the nose rather than in the brain, and it is often more treatable.
Epilepsy and Seizure Auras
Phantom smells can be the opening act of a seizure. In temporal lobe epilepsy, the brain region most involved in processing smell and memory, an “olfactory aura” can occur in the seconds or minutes before a seizure. A study of patients with temporal lobe epilepsy found that about 5.5% experienced olfactory auras, almost all of which were described as unpleasant. Neuroimaging in these patients showed that structural abnormalities typically involved the deep, inner parts of the temporal lobe, particularly the amygdala.7PubMed. Olfactory auras in patients with temporal lobe epilepsy
The mechanism involves repeated electrical discharges in the piriform cortex, a region deeply wired into smell processing. As excitability builds in these limbic areas, the brain can generate a vivid smell experience with no external trigger.8European Psychiatry. The bed smells like oil: About a case with diagnosis of epilepsy What makes seizure-related phantom smells distinctive is their brevity and repetition: they tend to last seconds to minutes, recur in a stereotyped pattern, and are sometimes followed by other neurological symptoms like déjà vu, altered awareness, or involuntary movements. If a phantom smell reliably precedes a headache, confusion, or loss of awareness, that pattern warrants urgent evaluation.
In rare cases, a new-onset phantom smell can be the first sign of a brain tumor. One case report described a previously healthy 70-year-old woman whose only initial symptoms were phantosmia and an abnormal taste; imaging revealed a glioblastoma.9PubMed Central. Phantosmia and dysgeusia as the first presentation of glioblastoma Cases like this are genuinely rare, but they illustrate why new, persistent phantom smells accompanied by other neurological changes deserve imaging.
Migraines and Phantom Smells
Migraines are famous for visual auras, the shimmering lines or blind spots that warn of an incoming headache. Olfactory auras are far less well known but do occur. A case report documented a patient who would smell burning, described as either cigarette smoke or trash, for about 30 minutes before her headaches arrived, followed by visual symptoms and then the migraine itself.10PubMed Central. Various presentations of the olfactory hallucination in two patients with migraine disease: Case report The temporal pattern here is the key diagnostic clue: the phantom smell reliably precedes the headache and resolves with it. If you only smell bleach or burning before or during migraines, the migraine itself is the likely culprit, and treating the migraine effectively can eliminate the phantom smells.
Head Injuries
Traumatic brain injuries are a recognized cause of both smell loss and phantom smells. The olfactory nerves sit in a vulnerable position at the base of the skull, where they can be sheared or bruised by impact. Research into head-injury-related olfactory changes has found that the mechanism involves metabolic shifts in both the olfactory system and the brain, including diminished growth factors that maintain olfactory nerve health and reduced levels of certain neurotransmitters. Correcting these abnormalities has been shown to improve smell loss, reduce phantosmia, and even improve cognitive function.11The FASEB Journal. Smell Loss and Onset of Phantosmia are Critical Aspects of Head Injury Cognition If your phantom smells began after a concussion, fall, or any blow to the head, the connection is worth raising with a doctor.
Neurodegenerative Diseases
Smell disturbances are among the earliest symptoms of Parkinson’s disease, often appearing years before the motor symptoms most people associate with the condition. Loss of smell gets the most attention, but phantom smells occur in Parkinson’s patients as well. A systematic review found that the frequency of olfactory hallucinations in Parkinson’s disease ranged widely across studies, from less than 1% to about 18%, and that women made up between 36% and 75% of affected patients depending on the study.12PubMed Central. Phantosmia in Parkinson’s Disease: A Systematic Review of the Phenomenology of Olfactory Hallucinations Alzheimer’s disease and other dementias can also involve phantom smells, though less research has focused on this aspect.
An isolated phantom bleach smell is not reason to panic about neurodegeneration. In Parkinson’s, olfactory hallucinations typically appear alongside other symptoms like reduced sense of smell, tremor, stiffness, or sleep disturbances. But for older adults experiencing new phantom smells in combination with cognitive changes or motor difficulties, it is a symptom worth mentioning at a medical appointment.
Medications and Psychiatric Conditions
Certain medications can trigger phantom smells as a side effect. One well-documented case involved topiramate, a drug used to treat epilepsy and migraines. A patient developed olfactory hallucinations after starting the medication, and the phantom smells stopped completely within two weeks of discontinuing it. The temporal relationship between starting the drug and the onset of symptoms, along with the resolution after stopping it, confirmed the medication as the cause.13European Psychiatry. Topiramate-Induced Phantosmia: A Case Report on Reversible Olfactory Hallucinations in Epilepsy Treatment Other medications that affect neurotransmitter systems can potentially do the same, so a new phantom smell that coincides with starting or changing a medication is always worth flagging.
Phantom smells also occur across several psychiatric conditions. A study comparing olfactory hallucinations across diagnostic groups found that about 35% of patients with schizophrenia reported them, along with 29% of patients with eating disorders and 19% of patients with depression.14PubMed. Olfactory hallucinations and olfactory identification ability in patients with schizophrenia and other psychiatric disorders The rates in depression and eating disorders surprised many clinicians, as olfactory hallucinations had traditionally been associated mainly with psychotic disorders. The phantom smells in these contexts are thought to arise from altered processing in the brain’s limbic system, the same networks that handle emotion and memory.
Why Chemical and Bleach-Like Smells Specifically
If phantom smells can produce any odor, why do so many people report chemical, burnt, or bleach-like sensations rather than, say, flowers or fresh bread? The answer has to do with how the brain categorizes smells. The piriform cortex, a key region for odor processing, organizes smells into categories partly through its internal associative connections. Research using a drug that disrupts these connections showed that interfering with the piriform cortex’s signaling scrambled the brain’s ability to distinguish between odor categories, and the degree of scrambling predicted how much people’s actual smell discrimination worsened.15PubMed Central. The role of piriform associative connections in odor categorization
When olfactory neurons misfire, they tend to produce signals that the brain interprets as “warning” smells: burnt, chemical, acrid, smoky. In the population-based study of older adults, the most commonly reported phantom smell by a wide margin was smoky or burnt, reported by nearly half of those with phantosmia.4Oxford University Press. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults It is not entirely clear why unpleasant and chemical-like smells dominate, but one theory is that the brain defaults to threat-signaling categories when it receives abnormal input, in the same way that random neural firing in the visual system tends to produce flashes or geometric patterns rather than coherent images. So smelling bleach fits the most common pattern for phantosmia: the brain, getting garbled signals, fills in the blank with something pungent and alarming.
Ruling Out Real Environmental Sources
Before assuming you have phantosmia, it is worth doing some detective work. Chloramine gas, which smells like bleach, can be produced when bleach-based cleaners mix with ammonia-based products or even urine. Residue from cleaning products can linger on surfaces and in drains for days. HVAC systems can circulate chemical fumes from one part of a building to another. A gas leak can sometimes smell chemical or acrid rather than like the classic rotten-egg scent of added mercaptan. Water with high chlorine content can produce a bleach-like smell, especially during hot showers when the chlorine volatilizes.
A few simple tests can help distinguish a real environmental odor from phantosmia. Ask someone else if they can smell it. Check whether it is present in multiple locations or only in one room. Notice whether it comes and goes with time of day, air temperature, or specific activities like running hot water. If other people can confirm the smell, or if it is confined to one physical location, you are probably dealing with an actual chemical source. Phantosmia tends to follow you everywhere, may be present on waking in the morning, and persists regardless of your environment.
When to See a Doctor
Most phantom smells are benign. The common post-viral variety typically improves gradually over months as olfactory neurons finish regenerating. But certain features should prompt medical evaluation:
- Accompanying symptoms: If phantom smells come with headaches, confusion, memory changes, involuntary movements, vision changes, or altered consciousness, neurological evaluation and imaging are warranted.
- Stereotyped episodes: If you experience the same brief smell repeatedly, followed by the same sequence of other symptoms, seizure activity should be investigated.
- Recent head trauma: New phantom smells after a concussion or head injury deserve follow-up, both because they can reflect brain changes and because treatment may help.
- Medication timing: If the smell started when you began a new medication or changed your dose, your prescriber should know.
- Persistent and worsening course: A phantom smell that gets stronger over weeks or months, especially in someone over 50, should be evaluated to rule out neurodegenerative or structural causes.
A doctor evaluating phantosmia will typically start with a thorough history (when did it start, is it one-sided, what triggers it, what relieves it) and a nasal examination. Depending on the clinical picture, imaging with MRI may be ordered to look at the temporal lobes and olfactory structures. Formal smell testing can help quantify how well the olfactory system is functioning overall.
The Emotional Weight of Phantom Smells
One aspect of phantosmia that tends to be underappreciated is how much it affects daily life and mental health. When researchers analyzed how people described their COVID-related phantom smells, nearly 78% of descriptions were classified as negative in sentiment. People with fluctuating smell dysfunction described their phantom smells even more negatively than those with permanent smell loss.5PubMed Central. Phantom smells: a prevalent COVID-19 symptom that progressively sets in The unpredictability may be part of what makes it so distressing: not knowing whether the next bite of food will taste right, or whether a phantom chemical smell will intrude during a work meeting.
Phantosmia can disrupt eating, since smell and taste are deeply linked, and people with persistent phantom smells sometimes lose weight or avoid foods that seem to trigger episodes. It can also produce anxiety, because smelling something that isn’t there is an unsettling experience that many people initially worry is a sign of serious illness or psychological breakdown. Just knowing the name for it, that it is a recognized medical phenomenon with identifiable causes, can reduce some of that anxiety. And for the many people whose phantom smells trace back to a viral infection or a nasal issue, the prognosis is generally good. The olfactory system has a remarkable capacity for repair, and for most people, phantom smells diminish with time even without specific treatment.