Phantosmia: Understanding Olfactory Hallucinations
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Phantosmia, commonly known as olfactory hallucinations, is a condition where an individual detects odors that are not present in their environment. While these phantom smells can occasionally be pleasant, they are most often described as foul or unpleasant, such as burning rubber or rotting food. Phantosmia is frequently a temporary symptom of common illnesses like sinus infections or allergies, though in rare cases, it can indicate underlying neurological issues. Most cases resolve once the primary cause is addressed.
Quick Answer
Phantosmia is a sensory disorder in which a person detects smells that do not exist in the environment. These phantom smells may affect one or both nostrils and be constant or intermittent. Common triggers include upper respiratory infections, nasal polyps and dental issues, while serious causes include migraines or Parkinson's disease. Treatment focuses on the underlying cause. nasal polyps migraines Parkinson’s disease [1]
What the research says
Phantom smells in Parkinson’s disease are real but under-recognized. A systematic review of 29 studies found that olfactory hallucinations affect between 0.5% and 18.2% of people with Parkinson’s disease, that 36% to 75% of those affected were women, and that the smells ranged from pleasant to unpleasant. Visual and auditory hallucinations often occurred alongside them (Ercoli et al., Neurol Int, 2024).
Doctors now use one agreed definition for phantosmia. An expert group of clinical olfactory researchers proposed standard definitions for eight smell terms, including phantosmia (also called olfactory hallucination), because the existing terms were vague and overlapping and made research hard to compare (Hernandez et al., ORL J Otorhinolaryngol Relat Spec, 2023).
In older adults, most smell distortions fade with time. A clinical review of age-related smell and taste changes reported that distortions and hallucinations are common in older persons and that most resolve over time, although this can take months or even years (Doty, Otolaryngol Clin North Am, 2018).
Research summaries are based on article abstracts retrieved from PubMed.
What Is Phantosmia?
Phantosmia (pronounced “fan-TAAZ-mee-uh”) occurs when the olfactory system generates a signal for a smell in the absence of any physical odor molecules. This phenomenon is distinct from parosmia, which is a distortion of a real, existing smell. In phantosmia, the brain perceives a scent that is entirely internal. It is a relatively rare condition, accounting for approximately 10% to 20% of all diagnosed smell disorders. [1]
For the majority of individuals, phantosmia is a temporary and benign condition. However, because the sense of smell is closely linked to the brain’s frontal lobe and olfactory bulb, persistent phantom smells can sometimes serve as an early warning sign for more complex medical issues. Understanding whether the smell is detected in one nostril or both is a critical detail for healthcare providers during the diagnostic process. [1] To learn more about how the smell pathway works, see our guide to the olfactory nerve.
What are the symptoms of phantosmia, and which odors are common?
The hallmark symptom of phantosmia is the detection of an odor that others in the same environment cannot perceive. While a small percentage of people experience pleasant phantom scents, such as the smell of flowers or baked goods, the vast majority report “cacosmia,” or foul-smelling hallucinations. [1]
Odor Category | Common Descriptions |
Combustion | Burning rubber, tobacco smoke, or burnt toast. |
Decay | Rotting food, garbage, or a moldy/stale scent. |
Chemical/Metallic | Harsh chemicals, ammonia, or a distinct metallic odor. |
Indistinct | Smells that are difficult to identify or have never been encountered before. |
What causes or triggers phantosmia?
Phantosmia is rarely a standalone condition; it is almost always a symptom of another underlying issue. These causes range from simple localized irritations in the nasal passages to systemic neurological disorders. [1]
Respiratory and Nasal Issues: Colds, sinus infections, allergies, and nasal polyps are the most frequent triggers. Inflammation in these areas can interfere with the olfactory receptors.
Environmental and Lifestyle Factors: Smoking, exposure to toxic chemicals like lead or mercury, and certain medications can induce phantom smells.
Dental Health: Gum disease or chronic dry mouth can sometimes manifest as an internal foul odor.
Neurological Conditions: In less common cases, phantosmia may be associated with migraines, head trauma, stroke, epilepsy, or neurodegenerative diseases such as Alzheimer’s and Parkinson’s. [1]
How is phantosmia diagnosed and tested?
To determine the root cause of olfactory hallucinations, healthcare providers perform a comprehensive evaluation of the ears, nose, head, and neck. They will typically ask for a detailed history of the phantom smells, including their duration, frequency, and whether they are unilateral (one nostril) or bilateral (both nostrils). [1]
If the cause is not immediately apparent, specialized tests may be ordered:
Nasal Endoscopy: A thin, flexible tube with a camera is used to inspect the nasal passages and sinuses for polyps or inflammation.
Imaging Tests: CT scans or MRIs can help visualize the brain and nasal structures to rule out tumors or structural abnormalities.
EEG (Electroencephalogram): This test measures brain activity and can help identify if the phantom smells are related to seizure activity or other neurological disorders. [1]
How is phantosmia managed, and what is recovery like?
Treatment for phantosmia is entirely dependent on the underlying cause identified during diagnosis. For most people, the phantom smells are temporary and will dissipate once the primary illness, such as a sinus infection or allergy, is resolved. [1]
Treatment Strategies
Resolving Infections: Antibiotics or antihistamines are used to treat the underlying respiratory or allergic condition.
Neurological Care: If the cause is brain-related, treatment may involve specialized medications for epilepsy or targeted therapies for tumors.
Home Relief: Nasal irrigation using a neti pot or saline solution can help clear the nasal passages and provide temporary relief. Over-the-counter nasal sprays may also be used to reduce congestion. [1]
Conclusion
While detecting smells that aren’t there can be a disorienting and sometimes distressing experience, phantosmia is usually a temporary symptom of a treatable condition. By identifying and addressing the root cause—whether it be a simple sinus infection or a more complex neurological trigger—most individuals can find relief and restore their normal sense of smell. If phantom odors persist for more than a few weeks, it is essential to seek a professional medical evaluation.
Related Reading
Frequently Asked Questions
What is the difference between phantosmia and parosmia?
Phantosmia is smelling something that isn’t there at all, while parosmia is a distortion where a real smell is perceived as something else, usually something foul.
Can stress cause phantom smells?
While stress is not a direct cause, it can exacerbate existing conditions like migraines or mood disorders, which may then trigger olfactory hallucinations.
How long does phantosmia usually last?
In most cases related to infections or allergies, it lasts only a few weeks. If the cause is neurological, the symptoms can persist for much longer, sometimes years.
Is smelling burnt toast a sign of a stroke?
While smelling burnt toast is a common description for a phantom smell, it is rarely the only sign of a stroke. However, any sudden olfactory hallucination should be evaluated by a doctor.
Can COVID-19 cause phantosmia?
Yes, many individuals have reported phantosmia or parosmia as a lingering symptom following a COVID-19 infection.
Are phantom smells always bad?
No, though it is less common, some people perceive pleasant scents like perfume or flowers. The majority, however, experience unpleasant odors.
Can a neti pot help with phantosmia?
Yes, nasal irrigation can help clear irritants and inflammation from the nasal passages, which may reduce the frequency of phantom smells.
Is phantosmia a mental health issue?
Generally, no. It is a sensory disorder. However, it can occasionally be a symptom of certain mental health conditions like schizophrenia.
When should I see a doctor about phantom smells?
You should consult a healthcare provider if the phantom smells persist for more than three weeks or are accompanied by other neurological symptoms.
References
Cleveland Clinic. Phantosmia. Cleveland Clinic Health Library. Last updated March 7, 2023. https://my.clevelandclinic.org/health/diseases/24799-phantosmia
Ercoli T, Bagella CF, Frau C, et al. Phantosmia in Parkinson’s disease: a systematic review of the phenomenology of olfactory hallucinations. Neurol Int. 2024;16(1):20-32. PMID: 38251050. DOI: 10.3390/neurolint16010002
Hernandez AK, Landis BN, Altundag A, et al. Olfactory nomenclature: an orchestrated effort to clarify terms and definitions of dysosmia, anosmia, hyposmia, normosmia, hyperosmia, olfactory intolerance, parosmia, and phantosmia/olfactory hallucination. ORL J Otorhinolaryngol Relat Spec. 2023;85(6):312-320. PMID: 37062268. DOI: 10.1159/000530211
Doty RL. Age-related deficits in taste and smell. Otolaryngol Clin North Am. 2018;51(4):815-825. PMID: 30001793. DOI: 10.1016/j.otc.2018.03.014
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.
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