Phantosmia: 8 things to know about olfactory hallucinations
February 16, 2026
Medically Reviewed | Last reviewed by Ehab Hanna, M.D., on February 16, 2026
Phantosmia is the scientific term for olfactory hallucinations — that is, the perception of odors that do not exist. It’s like detecting the aroma of coffee brewing at home when no one is making it, or smelling the scent of roses at work when no one is wearing perfume or has flowers at their desk.
Here, I’ll explore what causes phantosmia, how it’s treated, and if it can ever be a sign of cancer.
Phantosmia is one of many possible olfactory conditions
The first thing to know about phantosmia is that it’s just one of several conditions that can affect the sense of smell.
- Phantosmia is when you detect odors that aren’t actually there.
- Cacosmia is when you smell something unpleasant that isn’t actually there.
- Hyposmia is when you smell things accurately, but at a lower intensity.
- Anosmia is the complete loss of your sense of smell.
Hyposmia is likely the most common of these because it occurs when people have colds or allergies.
A brief overview of olfaction
The second thing to know is that the sense of olfaction is a complicated and intricate mechanism. So, it’s helpful to understand how it works.
Aromas are generated by airborne scent molecules that emanate from a given substance. When inhaled, they land on special receptors in the nasal lining, or mucosa. From there, they are carried across the nasal cavity, through the cribriform plate (a structure at the skull base that looks like a sieve), and into the frontal lobe of the brain to the olfactory bulb, where we actually perceive odors.
So, what causes phantosmia?
Anything that obstructs the nose can theoretically prevent scent molecules from reaching the olfactory area I just described. So, it’s pretty common for blockages to cause hyposmia or anosmia. But it’s far less common for those blockages to cause phantosmia.
You probably won’t be able to smell things normally, for instance, if you develop nasal polyps or a stopped up nose. Some of the secretions there may also give you an altered sense of smell, as if you’re smelling the mucus itself. But it’s pretty rare for an obstruction to cause phantosmia.
Generally speaking, the most common causes of phantosmia are:
- Viral infections, such as a really nasty cold or COVID-19
- Neurodegenerative disorders, such as multiple sclerosis
- Seizure disorders, such as epilepsy
- Head injury, which could be from an auto accident, sports-related concussion or other trauma
- Migraine headaches, which can also cause visual hallucinations, known as “auras”
Is phantosmia ever a sign of cancer?
Occasionally, tumors do alter the anatomy of the olfactory region, which can result in phantosmia as a symptom. But I don’t want anyone worrying about this. Statistically speaking, phantosmia is far, far more likely to be caused by something else.
Rarely, phantosmia does happen due to a tumor, such as an olfactory groove meningioma, a type of brain tumor that’s usually benign. Tumors may also spread to the olfactory grooves from somewhere else. The nasal and sinus areas are located right below the skull base, while the brain is located just above it. So, theoretically, the problem could originate from either of those directions.
Key takeaways
- Phanstomia is the scientific name for olfactory hallucinations, or perceiving smells that do not exist.
- It can be caused by many different things, most of which are not cancer.
- Phantosmia is usually temporary.
Do certain phantom smells ever denote particular ailments?
No. I don’t think anyone can definitively say, “If you smell burning rubber, you probably have this.” But when people hallucinate smells, unfortunately, they’re not usually very pleasant. So, instead of flowers or perfume or cookies baking, they’ll report things like rotting garbage, burnt toast or cigarette smoke.
How is phantosmia usually diagnosed?
If you have it, and it can’t be explained by a recent cold or respiratory virus, you might need a workup from an ear, nose and throat doctor (ENT) or a head and neck specialist. That’s especially true if it lingers more than two or three weeks. Phantosmia is usually temporary, even after a really nasty infection.
During the workup, we’ll ask you questions like, “Have you had COVID recently?” and “Do you ever have migraines?” Then we’ll do a series of tests and scans, including:
- Nasal endoscopy: This is when a tiny camera is passed through your nose to look at the olfactory region.
- MRI or some other imaging: We’ll use this to look more closely at the frontal lobe of your brain.
- Electroencephalogram (EEG): This analyzes the brain’s electrical activity to check for a seizure disorder.
If there’s no obvious reason for the phantosmia and we’ve gone down the list to rule everything out, it could just be idiopathic. That means we don’t know what’s causing it. In that situation, we would just leave it at that and wait to see if it stops on its own or any other symptoms develop.
How is phantosmia typically treated?
Treatment depends on what’s causing it.
- Sinusitis, rhinitis and other inflammatory conditions can be treated with antihistamines, decongestants and possibly steroids.
- Viral infections can be treated with antiviral medications.
- Bacterial infections can be treated with antibiotics.
- Polyps and tumors can be removed surgically or treated with other therapies to shrink them.
But in this case, the diagnosis is almost more important than the treatment. You have to treat the underlying cause, not just relieve the symptom.
Request an appointment at MD Anderson online or call 1-877-632-6789.
Phantosmia is usually temporary.
Ehab Hanna, M.D.
Physician