Loss of Smell and Taste: Causes, Treatment & Recovery

What Causes Loss of Smell and Taste?

The most common causes of smell and taste loss are nasal congestion and swollen nasal mucosa from viral infections (including COVID-19, influenza, and common cold) or allergies. Other causes include nasal polyps, head trauma, certain medications, smoking, nerve damage, and age-related decline. In many cases, no clear cause can be identified.

Understanding the underlying cause of smell and taste loss is essential for determining the appropriate treatment and predicting recovery. The olfactory system - our sense of smell - is remarkably complex, involving specialized nerve cells in the upper part of the nasal cavity that send signals directly to the brain. Any disruption along this pathway can affect our ability to smell.

What many people don't realize is that the majority of what we perceive as "taste" is actually detected by our sense of smell. The tongue can only detect five basic tastes: sweet, sour, salty, bitter, and umami (savory). All the rich complexity of flavor - the difference between an apple and a pear, or between different types of cheese - comes from the aromatic compounds detected by our olfactory system. This is why people with smell loss often report that food tastes bland or "like cardboard."

Smell and taste disorders can be classified based on their cause into two main categories: conductive loss, where something physically blocks odor molecules from reaching the smell receptors (such as nasal congestion or polyps), and sensorineural loss, where the smell receptors or nerves themselves are damaged (such as after a viral infection or head injury). Treatment approaches differ significantly depending on the underlying mechanism.

Viral Infections - The Most Common Cause

Upper respiratory viral infections are the leading cause of acquired smell loss, accounting for approximately 20-40% of all cases. This includes common colds, influenza, and most notably in recent years, COVID-19. When a virus infects the nasal passages, it can damage the delicate olfactory epithelium - the specialized tissue containing smell receptor cells - or cause inflammation that disrupts normal function.

COVID-19 has brought unprecedented attention to olfactory dysfunction. Studies show that 50-80% of people infected with SARS-CoV-2 experience some degree of smell or taste loss. What makes COVID-related smell loss unique is that it often occurs without significant nasal congestion, suggesting the virus directly damages the supporting cells in the olfactory epithelium rather than simply blocking airflow.

The good news is that the olfactory epithelium has remarkable regenerative capacity. Unlike most neurons in the body, olfactory receptor neurons can regenerate throughout life. However, this regeneration takes time, which is why recovery from post-viral smell loss can take weeks to months.

Nasal and Sinus Conditions

Chronic nasal and sinus conditions represent another major category of smell loss causes. Chronic rhinosinusitis - persistent inflammation of the nasal passages and sinuses - can impair smell through both mechanical obstruction and inflammation of the olfactory region. Nasal polyps, which are non-cancerous growths that develop from the nasal lining, can physically block the flow of air to the olfactory area in the upper nose.

Allergic rhinitis (hay fever) causes swelling and excess mucus production that can temporarily impair smell. The condition called vasomotor rhinitis - chronic nasal congestion without an allergic cause - can have similar effects. Unlike post-viral loss, smell impairment from these conditions often fluctuates and may improve when the underlying inflammation is treated.

Other Important Causes

Head trauma is a significant cause of smell loss, particularly if the injury involves the front of the head. The olfactory nerves pass through small holes in the skull base (the cribriform plate) and can be sheared during impact. Unfortunately, smell loss from head trauma often has a poorer prognosis than other causes.

Age-related decline affects approximately half of people over 65 and the majority of those over 80. This decline is gradual and represents the cumulative effect of reduced regeneration of olfactory neurons over time. While this natural decline cannot be reversed, awareness of it can help older adults take appropriate safety precautions.

Medications can affect smell and taste as a side effect. These include certain antibiotics, blood pressure medications, and chemotherapy drugs. Smoking damages the olfactory epithelium and is associated with reduced smell function - fortunately, this often improves after smoking cessation.

• Viral infections: COVID-19, influenza, common cold - accounts for 20-40% of cases
• Nasal/sinus disease: Chronic rhinosinusitis, nasal polyps, allergies
• Head trauma: Damage to olfactory nerves, often has poorer prognosis
• Age-related: Affects 50%+ of people over 65
• Medications: Certain antibiotics, blood pressure drugs, chemotherapy
• Smoking: Damages olfactory epithelium - may improve after quitting
• Neurological conditions: Early symptom of Parkinson's, Alzheimer's disease

Will My Sense of Smell and Taste Come Back?

Most people recover their sense of smell and taste after viral infections, though the timeline varies from weeks to months. Recovery rates are highest (80-90%) for post-viral loss when it resolves within 6-12 months. Factors affecting recovery include cause, severity of initial loss, age, and whether smell training is performed. Some cases may result in partial or permanent loss.

The prognosis for smell and taste recovery depends significantly on the underlying cause. Understanding what to expect can help manage anxiety about the condition and inform decisions about seeking treatment. The uncertainty of not knowing when - or if - these senses will return can be one of the most challenging aspects of olfactory dysfunction.

For post-viral smell loss, the outlook is generally favorable. Studies consistently show that approximately 80-90% of patients recover meaningful smell function within 6-12 months. The COVID-19 pandemic has generated extensive research on this topic. Most people with COVID-related smell loss recover within 2-4 weeks, though approximately 10-20% experience symptoms lasting several months or longer.

Recovery often doesn't happen all at once. Many people first notice a return of some smells before others, and the perception may initially be distorted or unpleasant (a condition called parosmia). This can actually be a sign that the olfactory system is regenerating, even if the experience is frustrating. Phantosmia - smelling odors that aren't present - can also occur during recovery.

Several factors influence the likelihood and speed of recovery:

• Severity of initial loss: Complete loss (anosmia) may take longer to recover than partial loss (hyposmia)
• Age: Younger individuals typically recover faster and more completely than older adults
• Duration before seeking treatment: Earlier intervention may improve outcomes
• Use of smell training: Active olfactory training significantly improves recovery rates
• Underlying cause: Viral causes generally have better prognosis than traumatic causes

For smell loss caused by nasal or sinus disease, the prognosis is often excellent with appropriate treatment. When nasal polyps or chronic sinusitis are effectively managed with medications or surgery, smell function frequently improves substantially. However, some degree of permanent olfactory epithelium damage may have occurred with longstanding disease.

Traumatic smell loss from head injury has a more variable prognosis. Studies suggest that 10-30% of patients recover some smell function, though complete recovery is less common. The degree of initial loss and the severity of the trauma are important predictive factors.

For age-related decline and smell loss due to neurodegenerative diseases, recovery is unfortunately unlikely as these represent progressive conditions. However, supportive strategies can help manage the practical and emotional impacts.

When Should You See a Doctor for Smell or Taste Loss?

See a doctor if smell or taste loss persists for more than 4 weeks, especially without other cold symptoms. Seek immediate medical attention if smell loss occurs after head trauma or is accompanied by neurological symptoms like confusion, vision changes, or weakness. Also consult a doctor if symptoms significantly impact your quality of life or safety.

While temporary smell and taste loss during a cold or respiratory infection is common and usually resolves on its own, certain situations warrant medical evaluation. Understanding when professional assessment is needed can help ensure appropriate care while avoiding unnecessary worry about self-limiting conditions.

Most acute viral infections cause smell impairment that resolves within 1-2 weeks as congestion improves. However, if you've had loss of smell or taste for more than 4 weeks, particularly without ongoing nasal congestion or other cold symptoms, a medical evaluation is recommended. This timeframe helps distinguish temporary dysfunction from conditions that may benefit from treatment.

Contact your healthcare provider promptly if you experience any of the following:

• Smell or taste loss lasting more than one month
• Persistent nasal congestion, facial pain, or pressure suggesting chronic sinusitis
• Recurring episodes of smell loss
• Gradual decline in smell function over time
• Distorted smell perception (parosmia) that significantly affects eating and quality of life
• Associated symptoms like nasal bleeding, visible nasal masses, or difficulty breathing through the nose

It's also worth seeking evaluation if smell or taste loss is significantly impacting your quality of life, nutrition, or safety. Many people with olfactory dysfunction experience depression, reduced enjoyment of food leading to poor nutrition, and anxiety about safety hazards they cannot detect (like gas leaks or smoke). A healthcare provider can help address these concerns and connect you with appropriate resources.

What Can You Do to Help Recovery?

The most effective self-help measure for smell loss is olfactory training (smell training) - systematically sniffing four distinct scents twice daily for 4-6 months. For congestion-related loss, nasal corticosteroid sprays can help. Quitting smoking improves olfactory function. Stay home when sick to prevent spreading infections that cause smell loss in others.

While some causes of smell and taste loss require medical treatment, there is much you can do on your own to support recovery and manage symptoms. Active participation in recovery through evidence-based self-care measures can significantly improve outcomes.

Managing Nasal Congestion

If your smell loss is accompanied by nasal congestion, addressing the congestion can help restore smell function. Over-the-counter decongestant nasal sprays can provide temporary relief if you're experiencing a cold. These work by reducing swelling in the nasal passages, allowing air (and odor molecules) to reach the olfactory area. However, use these only according to package instructions and for no more than 10 days, as prolonged use can cause rebound congestion that becomes difficult to treat.

Corticosteroid nasal sprays are available over-the-counter and can be used for longer periods. These reduce inflammation in the nasal lining and are particularly helpful if allergies or chronic rhinitis are contributing to your symptoms. Unlike decongestant sprays, corticosteroid sprays can be used safely for extended periods.

If you suspect allergies are contributing to your symptoms, over-the-counter antihistamines may help. Identifying and avoiding allergen exposure can also improve symptoms.

Quit Smoking

If you smoke, quitting is one of the most impactful steps you can take for your olfactory health. Smoking damages the olfactory epithelium and is associated with reduced smell function. The good news is that smell function often improves after smoking cessation, though recovery may take months to years depending on how long and heavily you smoked.

Olfactory Training (Smell Training)

Smell training is the most evidence-based self-help intervention for post-viral and other causes of smell loss. Multiple randomized controlled trials have demonstrated that systematic olfactory training significantly improves recovery rates compared to no treatment. The technique takes advantage of the olfactory system's capacity for neuroplasticity and regeneration.

Here's how to perform smell training effectively:

1. Gather four distinct scents: The classic protocol uses rose, lemon, clove, and eucalyptus. You can use essential oils on cotton pads in small jars, or household items with these scents. The key is choosing strong, distinct odors.
2. Smell each scent for 20 seconds: Hold the jar close to your nose and take gentle sniffs. While smelling, actively try to remember what the scent should smell like - engaging your memory and concentration appears to enhance the training effect.
3. Rest 10-30 seconds between scents: This prevents adaptation and ensures each scent is experienced fresh.
4. Repeat twice daily: Morning and evening sessions are recommended. Consistency is more important than duration.
5. Continue for at least 4-6 months: Research shows benefits typically emerge after several months of regular practice. Some studies suggest changing the scents every 12 weeks may provide additional benefit.

Don't be discouraged if you can't smell anything at first - the goal is to stimulate the olfactory system even if perception is absent. Many people begin to notice subtle improvements after several weeks of consistent practice. Keep a journal to track any changes, as improvements can be gradual and easy to overlook.

Stay Home When Sick

If you have a respiratory infection, staying home until you feel better helps prevent spreading the illness to others - potentially saving them from experiencing smell loss as well. This is particularly important given how commonly viral infections cause olfactory dysfunction.

How Is Smell and Taste Loss Diagnosed?

Diagnosis begins with a detailed medical history and physical examination, including nasal endoscopy to examine the nasal passages. Standardized smell tests can quantify olfactory function. Allergy testing may be performed if allergies are suspected. MRI or CT scans may be ordered to evaluate for structural problems, nasal polyps, or neurological causes.

A thorough diagnostic evaluation is important for determining the underlying cause of smell and taste loss and guiding appropriate treatment. The evaluation typically begins with your primary care provider and may involve referral to an otolaryngologist (ENT specialist) or neurologist depending on the suspected cause.

Medical History and Physical Examination

Your doctor will ask detailed questions about your symptoms, including when they started, whether the onset was sudden or gradual, any associated symptoms, and potential triggers or exposures. Information about recent respiratory infections, head injuries, medications, smoking history, and any neurological symptoms is particularly important.

Physical examination typically includes assessment of the nasal passages. Nasal endoscopy - using a thin, flexible scope with a camera - allows visualization of the nasal cavity, nasal septum, and the opening to the sinuses. This can identify nasal polyps, significant septal deviation, tumors, or signs of chronic inflammation that might be affecting smell function.

Smell Testing

Standardized smell identification tests can quantify the degree of olfactory dysfunction. These tests typically involve identifying a series of familiar odors from scratch-and-sniff cards or similar presentations. The results help classify the loss as complete (anosmia), partial (hyposmia), or within normal range, and can serve as a baseline for monitoring recovery.

More sophisticated testing in specialized centers may include threshold tests (detecting the lowest concentration of an odor) and discrimination tests (distinguishing between different odors).

Additional Testing

Allergy testing (skin prick tests or blood tests for specific IgE antibodies) may be recommended if allergic rhinitis is suspected as a contributing factor.

Imaging studies such as CT scans or MRI may be ordered to evaluate for structural abnormalities, chronic sinusitis, nasal polyps, or to assess the olfactory bulbs and related brain structures. MRI is particularly useful when neurological causes are suspected.

In some cases, referral to a neurologist may be recommended, particularly if the smell loss is unexplained, associated with other neurological symptoms, or if there's concern about possible neurodegenerative disease. Since olfactory dysfunction can be an early sign of Parkinson's disease or Alzheimer's disease (appearing years before other symptoms), evaluation in certain clinical contexts may include neurological assessment.

How Is Smell and Taste Loss Treated?

Treatment depends on the underlying cause. Nasal corticosteroid sprays are first-line for inflammatory causes. Allergies are treated with antihistamines and allergen avoidance. Sinus disease may require medication or surgery. Olfactory training is recommended for all patients with post-viral or idiopathic smell loss. When caused by age or nerve damage, treatment focuses on coping strategies and safety measures.

The treatment approach for smell and taste loss varies considerably depending on the underlying cause. A targeted approach addressing the specific mechanism of dysfunction provides the best chance of recovery. For some conditions, effective treatment can fully restore smell function; for others, management focuses on maximizing any remaining function and adapting to the loss.

Treating Nasal and Sinus Conditions

When smell loss results from nasal or sinus inflammation, corticosteroid treatment is typically the first-line approach. Intranasal corticosteroid sprays reduce inflammation in the nasal mucosa and can improve smell function when inflammatory conditions are present. These are available both over-the-counter and by prescription, with prescription formulations often being more potent.

For more severe inflammation, particularly in chronic rhinosinusitis with nasal polyps, oral corticosteroid courses may be prescribed. These provide more powerful anti-inflammatory effects but are typically used only for short periods due to potential side effects with long-term use. The improvement in smell during and shortly after an oral steroid course can help confirm an inflammatory cause.

If allergies are identified as a contributing factor, treatment includes antihistamines, allergen avoidance, and potentially immunotherapy (allergy shots or sublingual tablets) for long-term management.

When chronic sinusitis or nasal polyps don't respond adequately to medical treatment, sinus surgery may be recommended. Endoscopic sinus surgery can remove polyps, improve sinus drainage, and improve delivery of topical medications. Many patients experience significant improvement in smell function following successful surgery, though continued medical management is typically necessary to prevent recurrence.

Treatment for Post-Viral Smell Loss

For smell loss following viral infections, there is no medication proven to speed recovery. However, olfactory training is strongly recommended based on multiple clinical trials demonstrating its effectiveness. As described in the self-care section, this involves systematically sniffing four distinct scents twice daily for several months.

Some clinicians recommend a trial of intranasal corticosteroids for post-viral smell loss, though evidence for this is less robust than for inflammatory conditions. Omega-3 fatty acid supplementation and vitamin A nasal drops have been studied with mixed results and are not currently standard recommendations.

For COVID-19-related smell loss specifically, research is ongoing into various treatments. Currently, olfactory training remains the evidence-based recommendation, though research continues into other potential therapies.

When Treatment Cannot Restore Smell

When smell and taste loss results from age-related changes, severe nerve damage from trauma, or neurodegenerative disease, treatment cannot restore the lost function. In these situations, care focuses on helping individuals adapt to their new reality and maintain quality of life.

Learning to adapt to reduced smell and taste involves several strategies. Visual and textural aspects of food become more important for eating enjoyment. Careful attention to food safety - including checking expiration dates and proper food storage - becomes essential since you can no longer smell spoiled food. Installing and maintaining smoke detectors and gas alarms is crucial for safety.

How to Live with Reduced Smell and Taste?

Living with smell and taste loss requires adapting daily routines for safety and quality of life. Install smoke and gas detectors, check food expiration dates carefully, and use timers when cooking. Focus on texture, temperature, and visual appeal of food. Seek psychological support if experiencing depression or grief. Connect with others who share similar experiences.

When smell and taste don't fully recover, the impact on daily life can be significant. People with olfactory dysfunction face challenges ranging from the inability to enjoy food to safety concerns about undetected hazards. The condition can also profoundly affect emotional wellbeing, with many experiencing feelings of loss, isolation, and depression. Developing coping strategies and seeking support can help maintain quality of life.

Safety Considerations

One of the most important aspects of living with smell loss is addressing safety hazards. Without the ability to smell smoke, gas leaks, or spoiled food, individuals must rely on other means of detection.

• Smoke detectors: Ensure working smoke detectors are installed throughout your home and test them regularly
• Gas detectors: If you use natural gas, install gas leak detectors
• Food safety: Check expiration dates carefully, follow food storage guidelines strictly, and when in doubt, throw it out
• Cooking safety: Use timers to prevent burning food and never leave cooking unattended
• Personal hygiene: Maintain regular hygiene routines even without feedback from smell; ask trusted others to alert you to any concerns

Adapting to Eating and Food

Food enjoyment changes significantly without smell, but there are ways to maintain pleasure in eating. Since basic tastes (sweet, sour, salty, bitter, umami) are detected by the tongue rather than the nose, these remain intact. Focusing on these basic taste qualities, as well as texture, temperature, and visual presentation, can help maintain eating enjoyment.

Some people find that their appreciation for spicy foods increases, as the trigeminal nerve (which detects spice, mint, and similar sensations) remains unaffected by olfactory loss. Experimenting with different textures, temperatures, and mild spices may help make meals more interesting.

Using memory and imagination while eating can also help. Looking at food and remembering how it used to smell and taste, or having someone describe the flavors, can engage the brain's flavor processing systems even when direct smell perception is absent.

Emotional and Psychological Support

The psychological impact of smell and taste loss is often underestimated. Many people experience grief over the loss of cherished sensory experiences - the smell of a loved one, favorite foods, flowers, or the ocean. Depression and anxiety are common, and the condition can affect social activities that revolve around eating.

Speaking with a mental health professional such as a psychologist or counselor can be helpful for processing these feelings and developing coping strategies. Support groups, including online communities of people with olfactory dysfunction, can provide valuable connection with others who understand the experience firsthand.

It's important for family members and friends to understand and acknowledge the significance of this loss, even though it's invisible to others. Support from loved ones can make a meaningful difference in coping with the condition.