Anosmia – Loss of Smell: Causes and Treatment
Anosmia is the complete loss of the sense of smell. It can be temporary or permanent and may result from infections, injuries, or neurological conditions.
Things worth knowing about "Anosmia"
Anosmia is the complete loss of the sense of smell. It can be temporary or permanent and may result from infections, injuries, or neurological conditions.
What is Anosmia?
Anosmia is the medical term for the complete inability to perceive smells. People affected by anosmia cannot detect any odors -- neither pleasant fragrances nor potentially dangerous smells such as smoke or gas. Anosmia differs from hyposmia, which refers to a reduced -- rather than absent -- sense of smell. Anosmia can be temporary or permanent and can significantly affect quality of life, nutrition, and personal safety.
Causes
Anosmia can result from a wide range of conditions, from mild to serious:
- Upper respiratory infections: The common cold, influenza, or COVID-19 can inflame the olfactory mucosa and lead to temporary or prolonged anosmia.
- Nasal and sinonasal conditions: A deviated nasal septum, nasal polyps, or chronic sinusitis can physically block airflow to the olfactory receptors.
- Head injuries: Traumatic brain injuries may damage the olfactory nerve or related brain regions.
- Neurological diseases: Conditions such as Parkinson's disease, Alzheimer's disease, and multiple sclerosis are frequently associated with smell disorders, often as early warning signs.
- Toxic exposure: Long-term exposure to certain chemicals or heavy metals can permanently damage olfactory cells.
- Congenital anosmia: In rare cases, such as Kallmann syndrome, the ability to smell is absent from birth.
- Medications and radiation therapy: Certain chemotherapy agents or radiation to the head and neck region can impair olfactory function.
Symptoms and Associated Complaints
The primary symptom of anosmia is the total inability to detect smells. Common associated complaints include:
- Reduced sense of taste (as smell and taste are closely interconnected)
- Loss of appetite and unintentional weight loss
- Reduced quality of life and emotional well-being
- Increased safety risks (inability to detect smoke, gas, or spoiled food)
- Depressive symptoms and social withdrawal
Diagnosis
Anosmia is typically diagnosed by an ENT (ear, nose, and throat) specialist or neurologist using the following methods:
- Smell testing (olfactometry): Standardized tests such as the Sniffin Sticks test assess smell threshold, discrimination, and identification.
- Nasal endoscopy (rhinoscopy): Examination of the nasal cavity for polyps, inflammation, or structural abnormalities.
- Imaging: MRI or CT scans of the head to rule out structural causes such as tumors or injuries.
- Blood tests: To exclude systemic diseases or nutritional deficiencies.
- Neurological examination: When a neurodegenerative condition is suspected.
Treatment
Treatment depends on the underlying cause of anosmia:
- Treating the underlying condition: For sinusitis or nasal polyps, corticosteroids (as nasal sprays or oral tablets) or surgical intervention may restore olfactory function.
- Smell training (olfactory training): Regular, structured exposure to specific scents (e.g., rose, eucalyptus, lemon, clove) promotes regeneration of olfactory nerve fibers and is considered the most effective approach for post-infectious anosmia.
- Vitamin A therapy: Some studies suggest that vitamin A may support regeneration of the olfactory epithelium.
- Nasal corticosteroids: Can reduce inflammation and help in cases of inflammatory anosmia.
- Post-COVID-19 anosmia: Smell training is the best-supported therapy; most patients recover partially or fully within weeks to months.
- Psychological support: For persistent anosmia affecting mental health and daily life, psychological counseling may be beneficial.
Prognosis
The outlook strongly depends on the cause. Post-infectious anosmia (e.g., following COVID-19 or a cold) resolves fully or partially in many cases, especially with early smell training. Anosmia caused by nerve damage or neurological disease tends to be more severe or permanent. Regular follow-up appointments with an ENT specialist are recommended.
References
- Hummel T, Whitcroft KL, Andrews P et al. - Position paper on olfactory dysfunction. Rhinology. 2017;54(Suppl 26):1-30.
- Parma V, Ohla K, Veldhuizen MG et al. - More than smells -- COVID-19 is associated with severe impairment of smell, taste, and chemesthesis. Chemical Senses. 2020;45(7):609-622.
- World Health Organization (WHO) - Post COVID-19 condition (Long COVID), Fact Sheet, 2023.
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