Phantosmia, Olfactory Hallucinations, or Phantom Odors, is a sensory (olfactory) disorder that causes a person to smell odours that are not actually present in the environment (phantom odours). The odours could be pleasant (e.g. freshly baked goods) or unpleasant (e.g. faeces, rotten food, and mould).

Read on to learn about the main causes and complications of phantosmia, whether you are at risk of developing phantosmia if you have/had COVID-19, how phantosmia differs from parosmia when to see a doctor and much more!

Introduction 

Definition of phantosmia

Also known as Olfactory Hallucinations, phantosmia¹ is a sensory (olfactory) disorder that causes a person to smell odors that are not actually present in the environment (phantom odors). The odors could be pleasant or unpleasant, and detected either frequently or constantly. 

Phantosmia vs. parosmia 

Phantosmia differs from parosmia, which causes a person to smell odours that are present in the environment in a distorted way.² Often, this means that otherwise pleasant odours, such as freshly brewed coffee, are perceived as unpleasant odours, such as sewage or garbage. 

Importance of the sense of smell

The sense of smell is incredibly important as it not only allows us to fully experience the world around us, but also influences our food choices, appetite, taste, and mood all whilst helping protect us from danger and hazardous substances (e.g. fires and gas leaks).²  Therefore, having phantosmia and one’s sense of smell altered and disrupted can have a huge impact on overall quality of life, leading to mental disorders such as anxiety and depression as well as social isolation and anhedonia (lack of interest in activities that were otherwise enjoyable) (to name a few). 

Prevalence and incidence of phantosmia 

Phantosmia is quite uncommon, accounting for only 10-20% of cases of olfactory disorders.²

Causes of phantosmia 

Phantosmia is usually idiopathic, meaning that it occurs without a known cause.² 

However, phantosmia can sometimes occur due to certain factors including: 

1. Neurological (brain-related) conditions 

Such as:¹

• Parkinson’s disease
• Brain tumors
• Traumatic brain injury
• Stroke
• Epilepsy
• Alzheimer’s disease
• Neuroblastoma
• Migraines
• Temporal lobe seizures 

2. Sinus and nasal issues 

Such as:¹ 

• Sinus infections 
• Nasal polyps (benign growths in nasal passages and sinuses)

3. Psychiatric and psychological disorders 

Such as:²

• Anxiety
• Depression
• Schizophrenia 

4. Certain medications

Such as:³

• Antidepressants: used to treat depression 
• Antidiabetic medications: used to treat diabetes 
• Antihyperlipidemic agents: used to treat hyperlipidemia by lowering cholesterol levels  
• Chemotherapeutic agents: used to treat cancer 
• Thyroid medications: used to treat thyroid problems 
• Antibiotics: used to treat bacterial infections 
• Proton pump inhibitors: used to treat acid reflux and gastroesophageal reflux disease (GERD)

5. Toxic exposure to chemicals 

Such as:¹

• Mercury 
• Lead 

Other factors 

Ageing, hypothyroidism, smoking, allergies, colds, and dental problems (e.g. gum disease and dry mouth) may also cause phantosmia.^1,2  How all these conditions, disorders, and illnesses lead to phantosmia is currently unknown. 

Interestingly, a 2021 study reported the presence of phantosmia in patients with coronavirus disease 2019 (COVID-19).⁴ The signs and symptoms of phantosmia were found to completely disappear once the patients recovered from the viral contagious disease, suggesting a potential role of COVID-19 in the progression and development of phantosmia. 

Signs and symptoms 

The main symptom¹ of phantosmia is smelling odors that are not actually present in the environment (phantom odors). 

The odours could be: 

1. Pleasant  

Such as:

• Freshly baked goods and sweets

2. Unpleasant 

These are more commonly detected and include: 

• Faeces
• Garbage
• Rotten food e.g. rotten eggs 
• Burnt food e.g. burnt toast 
• Burning rubber
• Mould
• Tobacco smoke
• Gas
• Chemicals
• Metal 

Diagnosis 

A healthcare provider will diagnose¹ a suspected patient with phantosmia by performing a series of tests in the following order:

1. Physical examination and medical history: the healthcare provider will examine the patient’s nose as well as ears, head, and neck. A thorough medical history check-up will also be performed to rule in or rule out certain conditions that may cause phantosmia including migraines, temporal lobe seizures, schizophrenia, and mental disorders, for example.  

2. Diagnostic tests: these may include:¹
   • Nasal endoscopy: the healthcare provider will insert a thin tube with a light and camera attached called an endoscope into the patient’s nose in order to examine nasal passages and sinuses 
   • Imaging tests e.g. computed tomography (CT)¹ to scan the paranasal sinuses, and/or magnetic resonance imaging (MRI)¹ to scan the brain
   • A CT scan will be helpful to rule in or rule out any nasal or sinus issues, while an MRI will identify any neurological conditions, if present.  
   • Electroencephalogram (EEG): the healthcare provider may use this device to measure the patient’s brain activity and thus determine whether the patient has any neurological conditions that may cause phantosmia, including epilepsy, Alzheimer’s disease, and traumatic brain injury

Management and treatment 

Management 

There are certain home remedies available that may help people with phantosmia manage¹ their symptoms, including: 

• Nasal irrigation: this home remedy involves rinsing the nasal passages with a neti pot¹ or saline solution
• Nasal sprays: such as oxymetazoline spray, which is especially helpful for de-blocking a stuffy nose (nasal congestion) 

Treatment 

The treatment¹ for phantosmia is a complex process as it depends primarily on the underlying cause. 

Phantosmia usually goes away in a few weeks and does not require any treatment if it is caused by colds, allergies, or infections. 

However, if caused by neurological conditions, symptoms may linger for years, and phantosmia treatment will vary depending on the cause of brain dysfunction. For example, epilepsy may be treated using medication and/or surgery, whilst treatment for brain tumours may require chemotherapy and/or radiotherapy. 

Prevention strategies 

Phantosmia cannot be prevented because it is usually a sign or symptom of other disorders and conditions such as those described in the ‘’Causes’’ section above. 

However, the risk¹ of developing phantosmia can be lowered by adopting healthy lifestyle habits such as: 

• Avoiding and/or stopping smoking
• Maintaining a strong immune system: to prevent colds
• Effectively managing allergies, illnesses, or disorders: consider consulting your healthcare provider to change your medication/s if you perceive phantom odours when taking them. 
• Optimising dental health and fixing any dental problems e.g. dry mouth or gum-related concerns 
• Washing hands frequently and maintaining good hygiene to prevent infections

When to see a doctor  

• See a doctor¹ if you develop signs and symptoms of phantosmia
• Symptoms of phantosmia last longer than a few weeks 
• Your symptoms worsen 

Summary 

Phantosmia is a sensory (olfactory) disorder that occurs when certain odours that are not present in the environment are perceived and detected. Patients with phantosmia often report smelling burnt odours such as burnt food (e.g. burnt toast) and burning rubber. However, although less common, fruity, musty, metallic, chemical and sweet odours have also been reported. 

Despite being uncommon, phantosmia can have a huge impact on quality of life and influence not only the sense of smell but also taste, mood, appetite, and relationships. 

Although most cases of phantosmia occur spontaneously (idiopathic), phantosmia can also be caused by: 

• Neurological conditions e.g. migraines, and Parkinson’s disease 
• Sinus and nasal issues e.g. sinusitis and COVID-19 
• Psychiatric and psychological disorders e.g. anxiety and depression 
• Certain medications e.g. antidepressants, and antibiotics 
• Toxic exposure to chemicals e.g. lead, and mercury 

Phantosmia is currently diagnosed via physical examination and thorough medical history check-up as well as diagnostic tests, including nasal endoscopy, CT and/or MRI scans, and/or electroencephalogram (EEG). 

Treatment for phantosmia varies depending on its underlying cause. No treatment is usually required for phantosmia if it develops as a result of colds, allergies, or infections as symptoms usually vanish in a few weeks. However, neurological conditions require a more complex and tailored treatment plan, with epilepsy for example requiring medication and/or surgery and brain tumour treatment involving chemotherapy and/or radiotherapy. 

Phantosmia cannot be prevented, but its risk can be lowered by:

• Avoiding and/or stopping smoking
• Maintaining good hygiene and a strong immune system 
• Effectively managing allergies, illnesses, and disorders 

See a doctor mainly if: 

• You develop any of the signs and symptoms of phantosmia 
• Symptoms of phantosmia worsen and last for more than a few weeks