Loss of Smell: Causes, Diagnosis & Treatment

Updated in July 2022

Loss of smell can be characterized by a total or partial loss of the ability to smell. This loss can temporary, as is noted during a cold or flu, or it can occur due to more serious or permanent conditions, like radiation exposure or tumors. 

Because the sense of smell is directly related to the sense of taste, many people who have anosmia may also have difficulty distinguishing specific tastes, although they will generally be able to identify sweet, salta, bitter or acidic tastes. 

The loss of smell can be classified as: 

  • Partial anosmia: This is the most common form of anosmia, and is usually a result of colds, flus or allergies. 
  • Permanent anosmia: This occurs mainly due to accidents that damage the olfactory nerves and often is uncurable. 

Anosmia diagnoses are confirmed by a family doctor or otolaryngologist through testing like diagnostic imaging and endoscopy. Treatment depends on the underlying cause. 

Imagem ilustrativa número 1

Main causes 

In most cases, a loss of smell is triggered by conditions that irritate the nasal mucosa, which interferes with the identification of smells. The most common causes of loss of smell are: 

  • Allergic and non-allergic rhinitis 
  • Sinusitis
  • Cold or flu
  • Exposure to or inhalation of cigarette smoke 
  • Craniocephalic trauma
  • The use of certain medications
  • Exposure to chemical products 

In addition, there are less frequent conditions that can result in anosmia, like nasal polyps, nasal deformities or the development of tumors. Some illnesses that affect the nerves or brain can also cause changes to smell, like Alzheimer’s, multiple sclerosis, epilepsy or brain tumors. 

Therefore, if you experience loss of smell for no obvious reason, you should see your doctor to identify a possible cause start treatment as necessary. 

Can COVID-19 lead to loss of smell? 

A loss of smell is one of the most common symptoms of COVID-19. It is often also accompanied by a loss of taste. It is important to monitor for all symptoms of COVID-19, like persistent cough, fever, excessive fatigue and headache. 

Usually, the loss os smell persists even after the infection has resolved, however smell often returns to normal within a few weeks or months. 

Confirming a diagnosis 

A diagnosis is usually confirmed by a family doctor or otolaryngologist. A work-up to reach a diagnosis involves a symptom assessment and health history, to evaluate whether another condition can be contributing to nasal irritation.

Depending on the assessment, the doctor may order additional testing, like a nasal endoscopy or MRI.

Treatment options

The treatment of anosmia varies greatly and depends on the underlying cause of it. The most common cause of anosmia, cold or flus, are usually managed with rest, hydration, anti-histamines, nasal decongestants or corticosteroids, and these will usually address the loss of smell. Anosmia caused by COVID-19 can be treated with the previously-mentioned interventions, being sure to quarantine to prevent transmission. Learn more about the symptoms and treatment of COVID-19 and what you can do to prevent it. 

Anosmia caused by a bacterial infection can be treated with antibiotics. In more serious situations, like a nasal obstruction or nerve damage, the doctor may refer you to another specialist, like a neurologist, to ensure the most appropriate treatment approach.