Loss of Sense of Smell or Anosmia (also known as anosphresia or olfactory anesthesia) can cause a great deal of distress for the sufferer. The condition in which there is a complete loss of smell is called anosmia. Your sense of smell is very important, without which it would be difficult to carry out daily tasks. If you experience a loss of sense of smell, you might not be able to enjoy your food, smell a perfume or get the scent of a flower. It can also happen that you might be unable to identify a gas leak or detect smoke from a fire if your sense of smell is hampered.

To understand the loss of the sense of smell, let us first try and understand how we smell?

How Smell Works

Your sense of taste and smell allows you to navigate through the chemical world. Just like hearing is the perception of sound and sight is the perception of light, smell, and taste are the way you perceive tiny molecules in the air and in food. 

Chemicals in odorous material enter your nasal passage when you breathe and reach the roof of the nasal cavity where nerve endings, specially designed for your sense of smell, reside. The tips of these nerve endings are filled with several hair-like structures, called cilia, that receive and recognize different odour molecules. The chemical causes stimulation of these sensory nerve endings (the cilia) which get activated, passing on the impulse to the brain, which recognizes the odour from the past memory stored in its cells. 

Interestingly, the arc of the sense of smell is the shortest since the top of the nose is in such close proximity to the brain and impulses flow to and fro very quickly. Compare this with a sensation from the tip of your toe to the brain and you will get an idea of how short the nerve impulse has to travel to stimulate the brain about the smell.

Your sense of smell is linked to memory - a particular smell taking one back to a particular event or occasion. 

Now that you know the basics of how your smell works, let’s take a look at the types, causes, signs and symptoms, diagnosis, and treatment of anosmia.

Subtypes of Anosmia

Anosmia, commonly known as smell blindness, is the inability to smell anything. Other smell disorders or subtypes of anosmia include:

  • Hyposmia is a reduced or decreased power of smell. It is a partial loss of sense of smell and can disturb your routine activities. 

  • Dysosmia refers to an unpleasant odour triggered by a specific environmental odour. 

    • Parosmia is a type of dysomia in which you cannot detect a full range of smells around you. It is another type of reduced ability to sense smell. 

    • Cacosmia is another disorder of smell which is a type of parosmia. This disorder is characterized by an abnormal sensation (usually bad or foul) of smell.

Causes of Anosmia

There are several medical conditions and local or general causes associated with the loss of sense of smell. These include:

  • Upper respiratory tract infections (URTI) such as a common cold

  • Chronic sinusitis (an infection of your sinuses), with or without nasal polyps (non-cancerous growths in the lining of your nasal passage)

  • A crooked nose or any other nose abnormality

  • Certain medications including antibiotics (drugs that are taken to relieve pain and fever)

  • Injury to the nose or head trauma

  • Brain tumours extending down into the nose

  • Exposure to harmful chemicals that cause a burning sensation in your nose

  • Radiotherapy of the head or the neck

  • Alcohol and drugs abuse

  • Conditions like Alzheimer's (a progressive disease that destroys your memory and thinking skills), Parkinsonism (a brain disorder that affects your movements), or Multiple Sclerosis (an auto-immune disease that affects your central nervous system)

  • Old age

Signs and Symptoms

When you develop anosmia, the first sign is the loss of smell. You may find it difficult to identify or pick all or certain smells, depending on the intensity of anosmia. You may also not recognize any warning odours in your immediate environment, which can be dangerous.

Another sign or symptom is the change in flavour of your food. This happens because the flavour of your food arises out of your combined ability to smell and taste; loss of sense of smell also affects the taste perception of the food you eat.

Diagnosis of Anosmia

If you experience a loss of sense of smell which is not primarily due to a cold or an allergy, seek advice from your ENT specialist. Your doctor will examine your nose to see if there is a nasal polyp growing inside your nose, or if there is an unidentified infection or any other condition which requires treatment.

Will Anosmia Get Better?

Symptoms of anosmia will improve on their own in most individuals, especially after a common cold.

In some cases, you require corrective treatments like: 

  • Decongestant nasal sprays help manage anosmia caused due to nasal irritation or nasal blockage.

  • Medical management of sinusitis involves treating your sinus infection. Sinusitis is the inflammation of your sinuses that causes nasal congestion and hence results in a sense of loss of smell. Anosmia can be a symptom of persistent sinusitis.

  • Surgical removal of polyps or tumours. Nasal polyps increase inflammation and cause a sense of loss of smell. 

  • Stop smoking which can hamper your ability to smell. 

  • Other specific treatments suggested by your doctor.

In COVID-19, the earliest and most commonly reported manifestation is a  temporary loss of smell. Loss of smell in coronavirus disease can occur alone or can be accompanied by other symptoms like dry cough. The mechanism by which anosmia develops in patients with COVID-19 is still unclear.

Consult your doctor if your loss of smell does not get better in 4 to 5 days after the onset of symptoms.

Disclaimer: This article is written by the Practitioner for informational and educational purposes only. The content presented on this page should not be considered as a substitute for medical expertise. Please "DO NOT SELF-MEDICATE" and seek professional help regarding any health conditions or concerns. Practo will not be responsible for any act or omission arising from the interpretation of the content present on this page.