Introduction
The sense of smell in humans is most important as it is associated with enjoying a new sensation, identifying potentially dangerous odors like smoke or spoiled milk, and getting reminded of past experiences. Loss of smell is a condition that needs to be addressed by an ENT (ear, nose, and throat) physician or otolaryngologist. For some, loss of smell could be a temporary condition, while in others, including many elderly, the loss of sense of smell may be a persistent issue. The loss of sense of smell can be either partial or complete.
How Does One Detect Smell?
Certain processes are involved in the detection of smell. Initially, a molecule released from a particular substance, like a fragrance from a flower, stimulates special nerve cells located high up in the nose called the olfactory cells. These nerve cells transmit the information to the brain, where the specific smell is detected. The sense of smell can be affected by nasal obstruction, nasal congestion, damage to the nerve cells, and so on. The ability to smell also has an influence on one’s ability to taste.
What Are the Causes of Hyposmia and Anosmia?
Causes of Hyposmia:
Hyposmia can occur due to the following reasons:
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Infections like flu.
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Allergies.
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A deviated nasal septum.
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Small growths that develop in the nose and sinuses (polyps).
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Smoking.
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Hormonal imbalance.
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Dental issues.
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Chronic (long-term) problems in the sinus.
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Medications like Ampicillin, and Tetracycline (antibiotics), antidepressants like Amitriptyline, and antihistamines like Loratadine.
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Chronic (long-term) exposure to certain chemicals.
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Radiation therapy for head and neck cancers.
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Tobacco smoking.
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The use of drugs like cocaine.
Causes of Anosmia:
A swelling in the nose or nasal blockage could hinder odors from traveling up to the nose. Anosmia can also occur due to an issue in the transmission of signals from the nose to the brain. Anosmia can occur due to the following reasons:
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Common cold and flu.
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Nasal congestion and nasal polyps.
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A deviated septum.
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Allergies.
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Sinusitis (infection of the sinus).
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Hypertension (elevated blood pressure).
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Smoking.
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Obesity.
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Traumatic brain injury and brain tumors.
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Certain medications like antibiotics and antihistamines.
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Sjogren’s syndrome (a disorder of the immune system characterized by dry eyes and dry mouth).
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Multiple sclerosis (a disease in which the immune system attacks the protective covering of the nerves).
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Parkinson’s disease (a central nervous system disorder that affects movement, often causing tremors).
What Are the Signs and Symptoms of Hyposmia and Anosmia?
The onset of symptoms of hyposmia can be either gradual or sudden. The loss of smell can be either partial or complete. It might also be accompanied by a loss of taste in which one is unable to detect if something is sweet, salty, sour, or bitter. Even pleasant smells or tastes may turn unpleasant.
The onset of symptoms of anosmia can also be either gradual or sudden. A complete loss of smell in anosmia may be preceded by a difference in the sense of smell of familiar substances.
How to Diagnose Hyposmia and Anosmia?
The diagnosis of hyposmia and anosmia includes the following:
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Initial ways of diagnosing hyposmia include a physical examination of the nasal passages, sinuses, and surrounding structures.
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A person will be inquired about their previous medical history, particularly that of upper respiratory problems, and also about the nature of the symptoms.
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An otolaryngologist may carry out nasal endoscopy. It is a procedure in which a thin, long tube with a camera is inserted to examine the nasal and sinus cavities for signs of any swelling, bleeding, pus discharge, blockages, enlarged nasal structures, a deviated nasal septum, or growths like polyps or a tumor.
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If these tests do not pick the cause, the physician may suggest taking an MRI (magnetic resonance imaging) scan to evaluate the areas in the brain that detects odors. Hyposmia or anosmia can be diagnosed with a scratch-and-sniff test or tests with ‘Sniffin sticks’. For example, these tests determine the extent of loss of smell in individuals with hyposmia.
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A sip, spit, and rinse test may be performed. It is a test in which chemicals are smeared on some areas of the tongue, and the lowest chemical strength one can recognize is measured.
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Computed tomography (CT) scan and X-ray of the skull also aid in diagnosing hyposmia and anosmia.
How Are Hyposmia and Anosmia Treated?
The following are the various treatment modalities:
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The treatment of hyposmia and anosmia depends on age, medical history, the severity of the condition, one’s preference, how long the condition will last, and one’s ability to tolerate specific therapies, procedures, or medicines.
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Treatment involves medications, surgery, and any appropriate therapy to treat the underlying condition that led to hyposmia or anosmia.
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Surgery may be recommended to correct the deviated nasal septum, nasal polyps, and other structural problems. Medications like steroids and antihistamines may be prescribed to reduce inflammation caused by an allergy or respiratory infection.
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Other treatment methods involve counseling, refraining from smoking, and change of medications that led to hyposmia and anosmia. One should not stop taking any medications without consulting a physician.
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Age-related anosmia and hyposmia may be challenging to treat. However, certain steps can be followed to ensure safe and pleasant living. Smoke alarms and fire detectors can be used at home or in the office to detect smoke or fire.
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If one is doubtful about the quality of the leftover food and is unable to detect the smell, then one should avoid consuming it.
What Are the Complications of Loss of Smell?
The sense of smell is the most important of all the senses. A loss of sense of smell can have a negative impact on one’s quality of life and can affect one’s ability to detect dangers like:
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Smoke or fire.
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Gas leakage.
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Poisonous chemicals and fumes.
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Spoiled food and beverages.
Loss of sense of smell was one of the most common symptoms of COVID-19 (coronavirus disease 2019) infection. Current research has found that coronavirus can cause a transient loss of sense of smell, but the condition is not permanent. The loss of sense of smell can be regained in approximately two to three weeks following COVID-19 infection.
Can Hyposmia and Anosmia Be Prevented?
Since hyposmia and anosmia are a consequence of many underlying health conditions, these cannot always be prevented. However, the risks can be minimized in the following ways:
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Refrain from smoking.
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Avoid exposure to toxic chemicals and environments.
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Wear protective gear while playing contact sports since hyposmia and anosmia can be caused by brain injuries.
Conclusion
The human olfactory (sense of smell) system can detect between 10.000 and 100 billion different types of odors. Partial loss of sense of smell is called hyposmia, while an incomplete ability to detect any odor is called anosmia. Various factors, like underlying health conditions, could cause hyposmia and anosmia. Treating these conditions can restore the sense of smell that was lost. However, age-related loss of sense of smell may be difficult to treat, which could affect one’s ability to detect dangerous smells. Such individuals should use protective detectors like fire alarms or smoke and gas detectors in their homes and offices. Packed foods should be checked for their expiry date, and leftover foods that appear to be stale or doubtful should not be consumed. One should consult an ENT (ear, nose, and throat) physician or an otolaryngologist if they experience hyposmia or anosmia.
