Definition

Anosmia refers to a complete loss of the sense of smell, rendering an individual unable to smell any odors. Hyposmia, or a diminished sense of smell, is more prevalent than anosmia. Anosmia has become a widespread symptom in recent years, particularly due to the COVID-19 pandemic. The duration of anosmia can be either permanent or temporary, depending on its underlying cause.

While the loss of smell does not indicate a severe condition, it is one of the most fundamental and significant senses, contributing greatly to the enjoyment of life. The sense of smell allows individuals to appreciate the aroma of food, flowers, and favorite perfumes. It also serves a crucial function in identifying potentially hazardous odors, acting as a warning system for dangers such as gas leaks, spoiled food, or fire.

Disruptions in the sense of smell can negatively impact a person's quality of life and may also indicate more serious health issues.

Causes

Anosmia can result from an obstruction that hinders airflow through the nose. The olfactory system, responsible for the sensation of smell, involves cells in the nasal mucous membrane that send information to the brain via nerves. Damage to this system leads to a loss of the sense of smell.

Several diseases or conditions can cause anosmia, including:

• Nasal congestion. Anosmia often appears suddenly and is typically temporary, caused by severe nasal congestion due to colds, allergies, or upper respiratory infections. These conditions can cause inflammation and swelling of the nasal mucous membranes, blocking odor particles from reaching the upper nasal cavity where the olfactory nerves are located.
• Aging. Anosmia can be a normal part of aging, usually starting after the age of 65, though the process may be accelerated in smokers or those with chronic nasal inflammation. In many elderly individuals, anosmia may persist.
• Head or nose injury.
• Radiation therapy, particularly in the treatment of head and neck cancers.
• Medical conditions affecting the nervous system. Smell disorders can be early symptoms of serious conditions such as Parkinson's disease, Alzheimer's disease, and other dementias.
• Exposure to certain chemicals, for example insecticides
• Use of certain medications, such as antibiotics and antihistamine 

Risk factor

Problems with the sense of smell tend to increase with age and are more prevalent in men than women. A 2010 study conducted in Berlin found that nearly a quarter of men aged 60 to 69 had smell disorders, while only about 11% of women in the same age group reported similar issues.

Several factors can increase the risk of anosmia, including:

• Diabetes mellitus
• High blood pressure (hypertension)
• Nutritional disorders, such as nutritional deficiencies or obesity
• Smoking
• Dental problems

Symptoms

Symptoms of anosmia may develop gradually or appear suddenly, including:

• Loss of sense of smell
• Loss of taste, as taste is closely linked to smell
• Nasal congestion
• Nasal inflammation
• Respiratory tract infections

Loss of smell often accompanies chronic sinusitis symptoms, such as recurrent infections, facial pain or pressure, nasal blockage, and runny nose.

Anosmia can also reduce the desire to eat and drink, as a functioning sense of smell is essential for enjoying food.

In the elderly with dementia, anosmia may be accompanied by other symptoms such as memory impairment, difficulty walking, tremors, and speech disorders.

Diagnosis

To diagnose anosmia, a doctor will take a detailed medical history and examine the inside of the nose using specialized tools to check for tumors or polyps that could cause smell problems or infections.

Further evaluation by an otorhinolaryngologist may be required to determine the cause of anosmia. Diagnostic imaging, such as MRI or CT scans, may be necessary to get a clearer view of the nasal area and rule out tumors.

Specialized tests can help assess the severity of the loss of smell.

Management

Management of anosmia begins with identifying the underlying cause. If anosmia results from nasal obstruction due to a cold or allergies, therapy is typically unnecessary as the condition usually resolves independently. Over-the-counter medications for nasal congestion, such as oxymetazoline, can be used short-term to clear the nasal passages.

If a blocked nose does not improve within a few days or worsens, it may be due to an infection or another medical condition causing persistent symptoms. In such cases, a doctor may prescribe antibiotics to combat the infection, and other spray or oral medications to reduce inflammation.

Surgery may be necessary to remove tumor growths or polyps, thereby repairing the blockage and restoring the sense of smell.

For permanent anosmia, treatment strategies include implementing environmental safety measures and installing appropriate chemical detectors at home to detect gas and carbon monoxide. Additional treatments may involve natural saline to rinse the sinus, smell-retaining therapy, and certain supplements.

Complications

Similar to other senses, the sense of smell plays a crucial role in daily life. It often alerts individuals to the presence of smoke, spoiled food, or dangerous gas leaks.

When the sense of smell is impaired, individuals may experience changes in eating habits, leading to weight loss. Food may no longer taste appealing, prompting the addition of excessive salt to enhance flavor, which can be problematic for those at risk of hypertension or kidney disease. Additionally, anosmia can impact mental health and lead to depression.

Prevention

Several measures can help prevent anosmia, including avoiding certain chemicals and medicines, refraining from smoking, and exercising caution during extreme sports, driving, or risky activities.

When to see a doctor?

For those experiencing anosmia, creating a safer environment is essential:

• If you have acid detector at your house, ensure the device is functioning properly
• Make sure cooking equipment and electronics are turned off if not used
• Carefully read the expiration dates in the label of the food 

If an unexplained loss of smell due to allergies or flu persists for several weeks, it is advisable to consult an otorhinolaryngologist.

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