What is Phantosmia? Smell Hallucinations, Causes, Treatment
Phantosmia is a phenomenon where an individual smells something that is not actually there. This phantom smell may affect one or both nostrils, and can be pleasant, neutral, or unpleasant. Most cases of phantosmia are unpleasant olfactory hallucinations (cacosmia), with people reporting the smell of burning, or something that is rotten or foul.
Causes of Phantosmia
Phantosmia is usually caused by an infection, and is common after a cold, the flu, or sinusitis. This may be a result of damage to the olfactory tissues. As those tissues heal, phantosmia usually resolves. Phantosmia may also result from smoking, dental problems, and exposure to certain chemicals, especially insecticides and solvents. Radiation treatment for head and neck cancer may also lead to phantosmia, which may be permanent. Nasal polyps (growths in the nose) can also cause phantosmia.
In some cases, phantosmia is a result of underlying neurological issues. As such, less common causes of phantom smells include:
- Migraines (some people experience phantom smells just before a migraine)
- Traumatic brain injury (TBI)
- Epilepsy (temporal lobe seizures)
- Brain tumors (which may originate in the olfactory nerve)
- Parkinson’s disease
- Depression and other psychiatric illnesses
Diagnosis of Phantosmia
Because the senses of taste and smell are easy to confuse, a patient presenting with phantosmia will undergo various tests to confirm the diagnosis. A physician will also want to determine if the smell is really a hallucination. As such, they will carry out a thorough examination of the patient’s head and neck, checking the nasal passages for obvious issues. They will close off each nostril in turn to detect smell transmission, and they may then refer the patient to a specialist called an otolaryngologist (an ear, nose, and throat doctor).
At the specialist, a patient may have a nasal endoscopy, where a thin, flexible tube with a camera on the end is inserted into the nose to visualize tissues that are hard to see on an external examination. If no obvious signs of trauma are found, the patient may then have an MRI (magnetic resonance imaging) scan, or a computerized tomography (CT) scan. These scans will show any signs of tumors, lesions, or other structural issues that might be causing phantosmia.
Treatment for Phantosmia
To treat phantosmia, it can help to irrigate the nasal passages with saline solution. This can provide temporary relief from the phantom smell. Special neti pots are available to make it easier to clean the inside of the nose.
In the case of ongoing infection, treatment with antibiotics or antiviral agents may help to shorten the duration of the infection and associated symptoms such as phantosmia. Other treatments may be prescribed if phantosmia is linked to migraine, epilepsy, Parkinson’s disease, depression or other mental health issue. And, in cases where the condition is attributed to a brain tumor, surgery, chemotherapy, and/or radiation therapy may be warranted.
Prognosis for Phantosmia
Phantosmia may arise and linger after an infection. In most cases it will resolve of its own accord within a few weeks. However, if the symptom is severe enough to affect appetite or to significantly reduce quality of life, or if it persists after several weeks, it is best to see a physician who can make a referral to a specialist for further tests. In some cases, phantosmia can be permanent. If you experience phantosmia and have not had a recent upper respiratory tract infection (such as a cold), it is best to consult a physician to rule out any serious underlying cause.