Anosmia (loss of sense of smell)

A complete or total loss of smell in a person is known as anosmia, but there are other kinds of dysfunctions related to the sense of smell as well. They are:

• Congenital anosmia: Those born without a sense of smell are classified into this category.
• Phantosmia: In this disorder, people report being able to smell something which isn't usually there. A common example of this is the smell of smoke or burnt toast.
• Hyposmia: A reduced sense of smell is known as hyposmia.
• Parosmia: A rarer disorder where a person senses the smell to be changing, or a false sense of smell where he or she describes even a pleasant smell to be unpleasant.

The nose and a certain area in the upper throat are equipped with cells containing receptors that enable us to smell things. When these receptors pick up a smell, they send a signal to the brain which identifies the smell and differentiates it from other smells for you. However, even the slightest breathing problem may affect the sense of smell.

As loss of sense of smell is in itself a symptom of various types of illnesses, a reduced perception or the complete loss of your olfactory senses is a sign one should not ignore. Further diagnosis can help reveal the underlying cause or disorder.

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While losing your sense of smell may not seem like a big problem, anosmia can take a toll on a person's daily life as their awareness is compromised. Emergency situations like a fire hazard, a gas leak, stale food or contaminated water may not even register in a person's mind, potentially putting him or her in a dangerous situation.

Some of the causes of anosmia include:

• Nasal congestion due to a common cold, allergies, sinusitis or inflamed sinuses, smoking or even extreme air pollution in the area.
• Blockage in the nasal passages due to cancerous tumours or nasal polyps (non-cancerous tumours), or deformities in the nasal septum such as a deviated septum.
• Neurological conditions such as Alzheimer's disease, Parkinson's disease, tumours in the brain, Huntington's disease that may affect the olfactory senses
• Medical conditions that affect the central nervous system, like multiple sclerosis (MS), epilepsy, schizophrenia and stroke may affect the sense of sense.
• Conditions that affect the production of hormones, like hypothyroidism.
• Chronic illness like diabetes and malnutrition or vitamin deficiencies can also have this effect.
• Brain injury or having undergone brain surgery can sometimes affect the sense of smell.
• In some cases, loss of sense of smell has also been reported due to using certain medicines, exposure to chemicals or radiation or even excessive alcohol consumption.
• Recently, researchers have also established anosmia as one of the symptoms of COVID-19 infection, caused by the SARS-CoV-2 coronavirus.
• It is very rare, but some people are known to be born without a sense of smell as well.

The most common cause behind the onset of anosmia or losing your sense of smell is a stuffy nose that is not allowing you to breathe properly. If a common cold persists or an allergic reaction doesn't get better within a week or two, you should visit a doctor to investigate any underlying reason for your condition.

An ENT doctor is the right person to go to for anything related to the nose or breathing. The doctor may ask you questions about the problems you have been having, and for how long. An accurate description of the problems you have been facing helps the doctor to deduce further in their clinical assessment. 

The doctor may perform a physical exam and require you to get a CT scan of your nose. An MRI scan, an X-ray of the skull or even a nasal endoscopy are some of the other tests that may be required to arrive at a proper diagnosis.

Nasal congestions, allergies or blocked sinuses are some of the common causes of losing one's sense of smell. There's no cure for some of these conditions, and they can return periodically. But using decongestants to help you to breathe better, or certain antibiotics can help relieve the symptoms and restore your sense of smell after a bout of sickness.

If there is a growth in the nasal passage or lining, like in the case of a nasal polyp, the doctor may recommend removing it surgically. If the condition has been brought on due to the use of certain medications, then stopping the medicines immediately or finding an alternative medication that doesn't harm your sense of smell can take care of the problem.

In some cases, particularly with neurological conditions, head injuries or advancing age, anosmia may not be reversible. Smoking or excessive drinking can also dull your sense of smell, and avoiding both these habits can also help restore your olfactory functions.

Those living with anosmia can learn to live more efficiently with the use of smoke alarms, fire detectors or practising extra caution with food and drinks, especially when outdoors or while travelling.