What is Ageusia?

Ageusia is a rare condition characterised by a complete loss of taste, affecting the ability to detect sweet, salty, bitter, sour, and umami flavours.¹ Patients may report either total loss or significant reduction in taste perception, which can impact nutrition, appetite, and overall quality of life.

Symptoms

Individuals with ageusia may notice:

• Inability to taste foods or beverages
• Reduced appetite
• Weight loss in prolonged cases
• Altered enjoyment of meals

Some patients may experience partial taste reduction (hypogeusia), where flavours are diminished rather than completely absent.

Causes of Ageusia

Multiple factors can lead to ageusia, including nerve damage, dietary deficiencies, systemic conditions, and poor oral hygiene.

Nerve damage

The nerves responsible for taste include:

• Glossopharyngeal nerve (cranial nerve IX): connects the tongue and throat to the brain
• Lingual nerve: carries taste signals from the anterior two-thirds of the tongue

Damage to these nerves may arise from trauma, infections, tumours, inflammation, or neurological disorders. Even mild inflammation in the head or neck can interfere with nerve function and impair taste.¹

Dietary deficiencies

Essential vitamins and minerals play a significant role in maintaining taste function:

• Zinc: crucial for taste perception and protecting gum tissue. Zinc deficiency can lead to inflammation and aggravate oral health problems, particularly in patients with type 2 diabetes²
• Folic acid (vitamin B9): deficiency has been linked to taste disturbances. Supplementation has been shown to restore bitter taste receptor function²
• Vitamin D: low levels are associated with sensory loss, especially in older adults. Individuals aged 70–80 with vitamin D deficiency have a 96% higher risk of taste loss²
• Vitamin E: acts as a cofactor in both the olfactory epithelium and taste buds, supporting the correct functioning of sensory systems²

These findings emphasise the importance of nutrition for maintaining normal taste function and overall health.

Systemic conditions

Systemic conditions, such as diabetes, autoimmune disorders, and neurological diseases, may contribute to inflammation or nerve dysfunction that impairs taste perception.¹

Poor oral hygiene

Neglecting oral care can lead to:

• Tooth decay
• Gum disease
• Dry mouth

These conditions can damage taste-sensitive tissues and nerves. A study of elderly hospitalised patients found that poor oral health, especially dry mouth and high bacterial load, correlated with reduced ability to taste sweet, salty, and sour flavours.³

Ageusia and COVID-19

During the early stages of the COVID-19 pandemic, loss of taste emerged as one of the most distinctive symptoms. Alongside fever, cough, and fatigue, many patients reported a sudden inability to taste, making ageusia a useful diagnostic clue even in mild or asymptomatic cases.⁴

Epidemiology and clinical significance

Ageusia has been widely reported in both acute COVID-19 infection and long COVID:

• A global review found 19% of patients continued to experience taste loss post-infection, with 14% reporting persistent anosmia⁵
• In a study of 500 COVID-19 patients, 43% reported significant reduction in taste, particularly younger individuals⁶
• Data from over 10 million participants across three national surveillance platforms identified ageusia as the most reliable symptom associated with positive SARS-CoV-2 tests⁷
• An 18-month follow-up of 1,266 hospitalised patients reported ageusia in 7.1% at admission, dropping to 1.36% at 18 months, indicating gradual recovery over time⁸

These studies highlight the high prevalence and clinical relevance of ageusia as an early marker of COVID-19.

Diagnostic significance

Ageusia often appears early in the disease course:

• In one study, patients noticed taste loss about two days after the onset of other symptoms
• For half of patients, ageusia appeared within the first 1–2 days; for others, within 4–5 days
• Taste loss lasted on average eight days⁹

Sudden loss of taste is far more common in COVID-19 than in influenza and often precedes classic symptoms such as cough or fever.9 In some regions, like Italy and the US, up to 70% of COVID-19 patients reported taste loss early in infection.¹⁰

Public health and epidemiological importance

Because ageusia is rare in the general population, clusters of sudden taste loss can act as sentinel events:

• Prompt early self-isolation
• Trigger diagnostic testing
• Allow health authorities to monitor virus spread

Tracking taste and smell disturbances can provide real-time insights into community-level transmission. This epidemiological value helped identify outbreaks and guide containment strategies during the pandemic.

Management of COVID-19-related ageusia

While most COVID-19-related taste loss resolves spontaneously, several strategies may aid recovery:

Nutritional support

Ensuring adequate intake of zinc, folic acid, vitamin D, and vitamin E may support taste recovery. Patients should maintain a balanced diet rich in vitamins, minerals, and protein.

Oral hygiene

Maintaining oral health helps reduce secondary oral infections and supports regeneration of taste receptor function:

• Regular brushing and flossing
• Antimicrobial mouthwashes if advised
• Management of dry mouth with saliva substitutes

Symptomatic and rehabilitation approaches

• Olfactory and gustatory training: repeated exposure to strong flavours may stimulate nerve regeneration
• Avoidance of irritants: spicy or acidic foods may worsen oral discomfort in some patients

Follow-up

Patients with persistent ageusia beyond four weeks may require evaluation by an ENT specialist or neurologist. Early intervention can improve outcomes and address co-existing conditions, such as neuropathy or systemic illness.

Prognosis

Most patients regain their sense of taste within one to two years post-infection.8 Recovery is often gradual, with partial improvement appearing within weeks. Persistent ageusia beyond 12 months is uncommon but may occur in individuals with underlying comorbidities or severe initial infection.

Summary

Ageusia, or complete loss of taste, became a hallmark symptom of COVID-19. It is caused by nerve damage, systemic illness, dietary deficiencies, and poor oral hygiene. Sudden taste loss during the pandemic often preceded other symptoms and served as a reliable diagnostic and public health marker.

Maintaining good nutrition, oral hygiene, and following post-COVID recovery advice are key to restoring taste function. Most patients experience gradual improvement, and early recognition of ageusia supports quicker isolation, testing, and care.