Anosmia, the complete loss of the ability to detect odors, differs from hyposmia, which is a partial reduction in smell sensitivity. While individuals with anosmia can still perceive basic tastes—such as sweet, salty, sour, and bitter—they often struggle to distinguish complex flavors. This is because flavor perception relies heavily on the sense of smell rather than taste buds alone. As a result, those with smell impairment frequently report diminished taste perception and reduced enjoyment of food.
Age-related decline in smell sensitivity typically begins around 60, with more pronounced changes occurring after 70.
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### **Causes of Anosmia**
Anosmia can result from various factors, including nasal blockages, inflammation, or damage to the olfactory system—the nerves and brain pathways responsible for smell. Common causes include:
- **Head injuries** (especially in young adults): Trauma, such as from car accidents, can sever or damage olfactory nerves, leading to permanent smell loss.
- **Viral infections** (e.g., influenza, COVID-19): Respiratory illnesses account for nearly 25% of smell disorders.
- **Neurodegenerative diseases** (e.g., Alzheimer’s): These can damage olfactory nerves, particularly in older adults.
- **Nasal and sinus conditions**: Allergies, chronic sinusitis, or tumors near the cribriform plate (a bone separating the nasal cavity from the brain) may obstruct or impair smell function.
- **Medications, radiation therapy, or rare congenital conditions** can also contribute to temporary or permanent anosmia.
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### **Anosmia as a Symptom of COVID-19**
Sudden loss of smell (or reduced sensitivity) has been recognized as an early and distinctive symptom of COVID-19, caused by the SARS-CoV-2 virus.
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### **When to Seek Medical Attention**
Immediate evaluation is recommended if anosmia follows:
- A head injury
- Neurological symptoms (e.g., confusion, memory loss)
- Sudden onset without a clear cause
Early diagnosis can help identify underlying conditions and guide appropriate treatment.
