Of all the hallucination types, smell is the one that catches people most off guard. There is no obvious cultural script for it. People often describe noticing a smell that nobody else seems to register — burning rubber, rotting meat, a perfume from childhood — and quietly wondering whether something is wrong with them. In medicine, this experience is called phantosmia: the perception of a smell with no external source.
Phantom smells are usually caused by ENT or neurological problems rather than psychiatric illness, but olfactory hallucinations do occur in schizophrenia and can carry distressing meaning for the person experiencing them.
What people smell
The catalogue of phantom smells reported in the literature is striking. Among the most common are:
- Burning — smoke, rubber, electrical fires
- Decay — rotting flesh, garbage, sewage
- Chemical — gasoline, ammonia, bleach
- Sweet — perfume, flowers, sugar
- Specific personal smells — a deceased relative's cologne, a childhood food
Unpleasant smells are reported much more often than pleasant ones, regardless of cause.
Causes outside schizophrenia
The most important point about olfactory hallucinations is that schizophrenia is far from the most common cause. A clinician seeing this symptom will usually start with an ENT and neurological evaluation. Common non-psychiatric causes include:
- Sinus disease and upper respiratory infections — by far the most common cause of phantosmia
- Head injury — damage to the olfactory nerve or its central processing
- Temporal lobe epilepsy — brief, stereotyped olfactory auras precede some seizures
- Migraine — olfactory aura is rare but recognised
- Parkinson's disease and other neurodegenerative conditions
- Brain tumours, particularly in the temporal lobe
- COVID-19 sequelae — parosmia (distorted smell) and phantosmia have become widely reported since 2020
- Medication side effects
The NIH National Institute on Deafness and Other Communication Disorders publishes useful patient information on smell disorders.
Olfactory hallucinations in schizophrenia
Reviews indicate that olfactory hallucinations occur in roughly 5–25% of people with schizophrenia, depending on how they are measured. They tend to coexist with other hallucinations and are often interpreted by the person within a delusional framework — for example, smelling rotting flesh and concluding that one's body is dying, or smelling poison and concluding that someone is trying to harm them.
A specific syndrome called olfactory reference syndrome involves the fixed belief that one is emitting a foul body odour that others can detect. It overlaps with obsessive-compulsive and delusional disorders and sometimes responds well to SSRIs alongside antipsychotics.
How they are evaluated
An evaluation typically includes:
- An ENT examination of the nasal passages and sinuses
- A neurological exam
- Often, brain imaging (MRI) and sometimes EEG
- A medication review
- A psychiatric assessment if no other cause is found or if the smells coexist with other psychotic symptoms
Treatment
Treatment depends on cause:
- Sinus problems — treating the underlying ENT issue often resolves phantosmia
- Epilepsy — antiepileptic medication
- Schizophrenia — antipsychotic medication, with the same expectations as for other positive symptoms
- Olfactory reference syndrome — SSRIs and CBT, sometimes with adjunct antipsychotic
- Post-viral phantosmia — often improves slowly over months; smell training (regular exposure to defined odours) has emerging evidence
Phantom smells appear suddenly with weakness, vision changes, severe headache, or seizures. These can signal a neurological emergency.
What it's like to live with
People living with persistent olfactory hallucinations often describe a pervasive sense that something is wrong — even when they intellectually know the smell isn't real. The experience can be exhausting, especially when the smell is one of decay or fire that the brain interprets as danger. Tracking when the smells appear (time of day, after specific foods, during stress) often reveals patterns that help with management.
What to remember
If you or someone you love is smelling things others don't, please don't assume it's psychiatric. Start with a primary care doctor or ENT specialist. The cause may be a sinus issue, a recent infection, a medication, or something else entirely fixable. If a workup points toward a psychiatric cause, that too is treatable, and the same medications used for voices generally help.
This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.