Phantosmia: Symptoms, Types, Causes and Treatment

Phantosmia, often called "phantom smells," is a fascinating but frequently distressing condition that causes people to perceive odors that aren't actually present in their environment. This qualitative olfactory dysfunction can be a standalone symptom or part of a broader spectrum of smell disorders. In recent years, especially with the rise in post-viral olfactory issues following COVID-19, phantosmia has gained significant attention from both researchers and clinicians. This comprehensive article explores the symptoms, types, causes, and treatment options for phantosmia, drawing on the latest scientific research and patient experiences.

Symptoms of Phantosmia

Phantosmia is more than just an odd quirk of the nose—it's a vivid, often disruptive experience that affects daily life. People with phantosmia report sensing smells that have no physical source. These phantom odors can range from mildly unpleasant to deeply offensive, sometimes causing significant distress, anxiety, or even impacting quality of life.

Symptom	Description	Emotional Impact	Source(s)
Phantom odors	Smelling odors when none are present	Commonly negative	2 4 6 9
Odor qualities	Burnt, smoky, chemical, rotten, metallic	Revulsion, disgust	4 6 9
Fluctuating	Symptoms can vary in intensity/duration	Unpredictability	2 4
Mental distress	Anxiety, distress, reduced quality of life	Significant impact	2 4 6

Table 1: Key Symptoms of Phantosmia

Common Phantom Odors

Phantosmia is typically characterized by the perception of unpleasant smells. Many patients describe these as burnt, smoky, chemical, rotten, or metallic. Specific references to "tobacco" are more common among non-smokers, and descriptions are often negatively valenced—upwards of 78% of patients report their experiences as unpleasant or even revolting 4 9. These perceptions can be so vivid that they disrupt eating, working, and social interactions.

Fluctuations and Triggers

The intensity and duration of phantosmia can fluctuate. Some sufferers experience continuous phantom smells, while others report episodes that come and go or are triggered by environmental changes, emotional stress, or even seemingly random events 2 4. The unpredictability of symptoms adds another layer of distress for patients.

Emotional and Psychological Impact

Living with phantosmia is not just a sensory challenge—it can also have a profound psychological impact. Feelings of disgust, anxiety, and even depression are common, especially when the condition persists for months or years. Many patients find it difficult to describe their experiences to others, leading to feelings of isolation 2 4 6.

Types of Phantosmia

Phantosmia is not a one-size-fits-all condition. Understanding its types can help clinicians tailor diagnosis and management strategies more effectively. The main differentiation is based on the origin of the abnormal smell perception, as well as whether the experience is unilateral (one nostril) or bilateral (both nostrils).

Type	Description	Diagnostic Features	Source(s)
Peripheral	Originates from olfactory receptors/neurons	Unilateral, modifiable by nasal maneuvers	5 6 13
Central	Arises from brain/olfactory pathway dysfunction	Bilateral, not affected by nasal maneuvers	5 6 7
Unirhinal	Affects one nostril (often cyclic)	May be initiated/inhibited, EEG changes	5 13
Birhinal	Involves both nostrils (often non-cyclic)	Usually after hyposmia, less modifiable	5

Table 2: Primary Types of Phantosmia

Peripheral vs. Central Phantosmia

• Peripheral Phantosmia: This type results from problems with the olfactory receptors or neurons in the nose—often following injury, infection, or other local issues. The phantom smell is typically localized to one nostril (unirhinal) and may be modifiable by physical interventions such as nostril occlusion or topical anesthesia. Peripheral phantosmia may improve with treatments targeting the olfactory mucosa 5 6 13.

• Central Phantosmia: Here, the issue lies within the central nervous system—specifically, in the brain’s olfactory processing centers. Symptoms are usually bilateral (birhinal) and are less likely to be influenced by local nasal interventions. Central phantosmia can be associated with neurological conditions, brain injury, or even as a side effect of treatments like radiation therapy 5 6 7.

Unirhinal and Birhinal Manifestations

• Unirhinal (One-Sided): These cases can sometimes be triggered by actions such as laughing, coughing, or even specific maneuvers. They may show specific EEG changes, suggesting a localized neural basis 5.
• Birhinal (Both Sides): More common and often seen in the context of generalized olfactory loss or damage. These do not respond to peripheral interventions and are thought to have a central origin 5.

Other Variants

Some patients may experience both types or a mixture, and there can be overlaps with other qualitative olfactory disorders such as parosmia (distorted odor perception in response to real odors) 2 3 5.

Causes of Phantosmia

Phantosmia can arise from a broad spectrum of causes, ranging from local nasal issues to systemic conditions affecting the brain. Understanding the underlying cause is critical for effective management.

Cause Category	Examples	Prevalence/Context	Source(s)
Post-viral	COVID-19, other respiratory infections	Increased post-pandemic	1 2 3 4
Trauma	Head injuries, nasal trauma	Not uncommon	3 5 6
Sinonasal disease	Chronic rhinosinusitis, polyps, tumors	10–20% of olfactory disorders	6 3 8 10
Neurological	Epilepsy, brain tumors, neurodegenerative diseases	Central phantosmia	5 7 10
Idiopathic	No identifiable cause	Up to 33% cases	3
Radiation therapy	Brain or ENT region radiation	Common during RT	7
Aging/genetics	Female gender, BDNF gene, vascular risk	4.9% in older adults	9

Table 3: Main Causes of Phantosmia

Post-Viral Causes

The COVID-19 pandemic has brought post-viral phantosmia into the spotlight. Many patients report developing phantom smells weeks or months after recovering from the acute phase of infection. These qualitative changes can persist for months and sometimes appear as delayed symptoms—long after the initial loss of smell or taste has resolved 1 2 4.

Sinonasal and Local Factors

Conditions that affect the nasal passages and olfactory mucosa—such as chronic rhinosinusitis, nasal polyps, or even tumors—can lead to phantosmia. In these cases, the disorder is usually peripheral in origin and may respond to treatments targeting the local pathology 6 8 10.

Trauma and Injury

Head injuries and nasal trauma can disrupt the olfactory pathways, leading to either loss or distortion of smell, including phantosmia. The onset may be immediate or delayed, depending on the extent and location of the injury 3 5 6.

Neurological and Central Causes

Phantosmia may arise from central nervous system disorders, including epilepsy, brain tumors, neurodegenerative diseases, and as a side effect of treatments like radiation therapy to the brain or ENT region. These forms are often bilateral and resistant to local nasal interventions 5 7 10.

Idiopathic and Other Factors

A significant percentage of cases remain idiopathic—without a clear underlying cause. Genetic factors (such as the BDNF gene), vascular risk, and female gender have been associated with a higher prevalence, especially in older adults 3 9.

Treatment of Phantosmia

Managing phantosmia is challenging, as treatments depend on the underlying cause and type. Options range from reassurance and self-management to medical therapies and, in select cases, surgical intervention.

Treatment Method	Description/Use Case	Effectiveness/Notes	Source(s)
Reassurance/Watchful waiting	Many cases resolve naturally	First-line for mild cases	3 8
Olfactory training	Repeated exposure to scents	Common self-help, variable benefit	3
Medications	Topical/systemic drugs, anesthesia	Limited success, used selectively	8 5
rTMS	Repetitive transcranial magnetic stimulation	Promising, requires further study	11
Surgery	Excision of olfactory mucosa	Effective for select peripheral cases	6 12 13
Addressing underlying cause	Treating infections, polyps, tumors	Essential in secondary phantosmia	6 8 10

Table 4: Treatment Options for Phantosmia

Conservative and Self-Management Approaches

• Reassurance and Monitoring: Many mild cases of phantosmia, especially those following viral infections, improve over time without intervention. Patients are often reassured and monitored 3 8.
• Olfactory Training: This involves daily exposure to a set of distinct scents and is the most commonly reported self-management strategy. Evidence is mixed, but some patients find it helpful 3.

Medical Therapies

• Medications: Topical or systemic drugs—such as corticosteroids, local anesthetics, or anticonvulsants—have been tried, but with limited success. In some cases, nasal anesthesia can temporarily relieve symptoms, particularly in peripheral phantosmia 5 8 13.
• Repetitive Transcranial Magnetic Stimulation (rTMS): This non-invasive brain stimulation technique has shown promise in small studies, with up to 88% of patients experiencing improvement in symptoms. However, repeated sessions may be necessary, and broad clinical adoption awaits further research 11.

Surgical Options

• Excision of Olfactory Mucosa: For severe, persistent, and well-localized peripheral phantosmia, surgical removal of the affected olfactory mucosa can be highly effective and preserve overall smell function. This is a specialized procedure with some risks and is reserved for cases that do not respond to other treatments 6 12 13.
• Other Surgical Interventions: Rarely, more invasive procedures such as olfactory bulbectomy have been considered, but these are now largely supplanted by targeted mucosal excision 13.

Addressing Underlying Conditions

When phantosmia is secondary to another condition—such as chronic sinus disease, tumors, or exposure to toxins—treating the primary issue is essential for symptom resolution 6 8 10.

Challenges and Future Directions

Despite growing research, there is still a lack of universally effective therapies for phantosmia. Many patients report receiving little or no treatment, highlighting a need for greater awareness, research, and support strategies 3 14.

Conclusion

Phantosmia is a complex and often distressing sensory disorder that can profoundly affect those who experience it. While recent research—especially in the context of COVID-19—has shone new light on its symptoms, types, and causes, effective treatment remains challenging. Here’s a summary of the main points:

• Symptoms: Phantom odors, often unpleasant, can fluctuate and cause significant distress 2 4 6 9.
• Types: Phantosmia can be peripheral (often unilateral and modifiable) or central (bilateral and resistant to local treatments) 5 6 13.
• Causes: Range from post-viral changes (notably post-COVID-19), trauma, sinonasal disease, neurological disorders, radiation therapy, to idiopathic factors 1 2 3 4 5 6 7 9 10.
• Treatment: Includes reassurance, olfactory training, medications, rTMS, and surgery for select cases; addressing any underlying cause is crucial 3 5 6 8 10 11 12 13.

Understanding phantosmia requires a multidisciplinary approach, combining patient-centered care with ongoing research. As science continues to unravel the mysteries of smell, there is hope for better therapies and improved quality of life for those affected by this perplexing condition.