Introduction

Ageusia is a condition in which an individual loses the sense of taste. The ability to distinguish between different flavours and foods declines and eventually diminishes. It must be distinguished from other taste disorders, including phantogeusia, in which taste perception occurs without any tastant present; dysgeusia, which involves unpleasant perception of a tastant; hypergeusia, where increased gustatory sensitivity is observed; and hypogeusia, which is characterised by decreased sensitivity to all tastants.

Scientists believe that numerous factors, such as infections, injuries, ageing, lifestyle, and smoking, may contribute to this condition.² It is most common in people over 50; however, complete loss of taste is infrequent. Data show that out of 1,000 individuals, fewer than 2 suffer complete loss, or true ageusia.²

Ageusia due to zinc deficiency

Zinc plays an important role in cellular function and is a trace element in human nutrition.³ Zinc is also essential for taste buds to function properly, and the association between taste disorders and zinc deficiency is well established.⁴ A deficiency of zinc can cause various immune-related issues, as well as being responsible for ageusia.^1,2 Gustin is a major zinc-containing protein, and a decrease in its levels disrupts salivary zinc concentrations, which alters taste bud function and eventually results in loss of taste.⁴ Zinc deficiency is the second most common reason for ageusia (14.5%), after medications (21.7%).

Symptoms

Although the primary symptom of ageusia is loss of taste, various other symptoms may arise, including:

• Nutrient deficiency
• Decreased appetite
• Weight loss
• Hypertension
• Allergies²

Causes

Various causes have been identified for ageusia, including infections such as COVID-19 and sinus infections, as well as conditions such as gum disease, diabetes, zinc deficiency, and vitamin B12 deficiency.⁴ The focus of this article is zinc-related ageusia, which is a reversible condition. Zinc deficiency can have a significant impact on the ageing process and may contribute to several age-related chronic disorders, including cancer, immune decline, cardiovascular disease, and neurodegenerative conditions.³

Diagnosis

Identification of ageusia is performed using several approaches:

• Taste tests: The mouth is exposed to liquids with various concentrations of sweet, sour, salty, or bitter flavours. The substance may be applied as a tablet, wafer, spray, drop, or flavour patch
• Imaging tests: If the loss of taste is caused by a structural problem in the head or neck, an imaging test such as a CT (computed tomography) scan or MRI (magnetic resonance imaging) may be required
• Lab tests: Blood tests may help medical professionals determine whether ageusia is caused by a vitamin or mineral deficiency²
• Psychophysical evaluation: This is vital in determining the degree of permanent taste loss and in assessing the patient's complaints. The patient's psychological condition must also be taken into consideration, as a taste disorder may cause depression, or depression may itself contribute to a taste complaint¹

Treatment

Zinc supplementation

To treat zinc-related ageusia, zinc supplements should be taken to address the deficiency. Zinc supplementation is an effective treatment for taste disorders in patients with zinc deficiency, idiopathic taste disorders, and in patients with taste disorders induced by chronic renal failure when given in high doses ranging from 68 to 86.7 mg/d for up to six months.⁴

Once zinc levels return to normal, the sense of taste gradually begins to recover, which is why the condition is termed reversible. Studies have shown that daily zinc supplementation improved antioxidant activity, reduced inflammation, and decreased the frequency of infections. Zinc also improved general immune function in older adults and those with conditions such as sickle cell anaemia or renal disease. These findings suggest that zinc may aid in taste recovery by reducing inflammation and encouraging cell repair. However, excessive zinc consumption can result in adverse effects such as fatigue, nausea, and blood cell abnormalities. Zinc supplements should therefore only be administered in cases of verified deficiency.³

Other treatments

Identifying and treating the underlying cause is the cornerstone of ageusia management. In some cases the condition resolves on its own, particularly when connected to transient causes such as viral infections or adverse drug reactions. When ageusia is caused by medications, particularly chemotherapy or radiation therapy, taste may return once the offending drug is removed. However, patients with severe conditions such as diabetes or cancer may not be able to discontinue the responsible medication. Alpha-lipoic acid (600 mg/day) and zinc gluconate (up to 140 mg/day) are two nutritional supplements that have shown potential in helping cancer patients regain their taste. Topical anaesthetics such as lidocaine gel can assist in treating severe taste disturbances, while medications such as clonazepam or tricyclic antidepressants may provide relief for conditions like burning mouth syndrome or dysgeusia. Antibiotics are used to treat infections, and taste function frequently returns once the infection is resolved. When ageusia is brought on by the flu or a cold, antihistamines or decongestants may be helpful.

Lifestyle changes and home remedies

Lifestyle modifications can also have a positive impact. For example, quitting smoking can restore taste in as little as 48 hours, and improved dental hygiene can reverse taste loss associated with gum disease. Some supportive measures individuals can take at home include:

• Giving up smoking
• Improving oral hygiene through regular use of medicated mouthwash, brushing, and flossing
• Using over-the-counter antihistamines or vaporisers to reduce nasal inflammation

Ultimately, restoring normal taste perception depends on addressing the underlying cause.⁵

Prognosis

The prognosis for people with ageusia is generally favourable, as the condition is frequently transient and reversible once the underlying cause is addressed. Most people recover their sense of taste within one to three weeks after contracting an infection such as influenza or COVID-19. When ageusia results from nutritional deficiencies, lifestyle factors, or medications, addressing these causes through dietary supplementation, medication adjustment, or smoking cessation can lead to notable improvements. Permanent loss of taste is rare. Treatment outcomes are, however, significantly influenced by the underlying cause, the promptness of diagnosis, and the patient's general health. Maintaining a healthy, balanced diet is important throughout recovery to support overall well-being. The loss of enjoyment in eating can also cause emotional distress or depression in some patients, which underscores the importance of supportive care and reassurance from healthcare professionals.

Summary

Ageusia is a rare but often reversible taste disorder, with zinc deficiency being one of its most manageable contributing causes. Prompt diagnosis and appropriate supplementation can restore taste function in many patients. Recovery also depends on identifying and treating any additional underlying factors, whether infectious, pharmacological, or lifestyle-related. With proper medical attention, nutritional support, and lifestyle modifications, most patients experience significant improvement or complete resolution of their symptoms.