Taste disorder (dysgeusia): causes, tests and what really helps

No taste anymore? Causes from post-Covid and zinc deficiency to medications and dental problems, tests, therapy and when to see a doctor.

1. What is a taste disorder?

A taste disorder — medically dysgeusia — describes any change in the normal perception of taste. This ranges from a slight impairment through a changed or distorted taste to a complete loss of taste (ageusia). Taste disorders are common — about 5 per cent of the population in Germany are persistently affected, from age 60 considerably more.

Important is the distinction between taste and smell disorders. Many people who complain of a loss of taste in reality have a smell disorder — the greatest part of our 'taste experience' when eating is actually smell, which reaches the nose retronasally (via the throat). Real isolated taste disorders — in which the taste buds themselves are affected — are rarer than smell disorders.

Taste disorders can considerably restrict quality of life: eating loses its appeal, which can lead to loss of appetite, weight loss and social withdrawal. Some of those affected experience persistently unpleasant tastes (metallic, bitter, salty) that make every bite a torment. At the same time, a taste disorder can be the early sign of serious conditions — from neurological disorders to tumours in the head and neck region.

2. How does the sense of taste work?

The sense of taste is, compared to the other senses, astonishingly simply built. On the tongue — and to a lesser extent on the palate and in the throat — there are about 2,000 to 5,000 taste buds that perceive in five basic taste directions: sweet, sour, salty, bitter and umami (savoury-spicy).

These five basic tastes are conducted to the brain via three different cranial nerves: the facial nerve (VII) for the front two thirds of the tongue, the glossopharyngeal nerve (IX) for the rear third and the vagus nerve (X) for the throat and the larynx region. The complex taste experience when eating only arises through the interplay with the sense of smell: while we chew, scent substances rise via the throat to the olfactory mucosa — the so-called retronasal perception. It makes up about 80 per cent of what we perceive as 'taste'.

From this follows the most important practical conclusion: anyone who can no longer distinguish coffee, wine, cheese or a seasoned dish almost always has a smell disorder — the taste buds distinguish only five basic qualities. Anyone who, by contrast, can no longer taste simple sweetness, sourness or saltiness has a real taste disorder. This distinction often only leads to the correct diagnosis in everyday clinical practice.

3. Forms of taste disorder

ENT medicine distinguishes several clinical forms that are diagnostically and therapeutically relevant in different ways:

• Ageusia: a complete loss of taste perception — very rare, almost always only in combination with a loss of smell
• Hypogeusia: reduced taste perception — the most common form, often setting in gradually
• Dysgeusia: changed or distorted taste perception — e.g. a metallic, bitter or soapy taste
• Parageusia: an unpleasant taste with normal stimulation — foods suddenly taste 'wrong'
• Phantogeusia: taste perception without an external stimulus — typically a persistently metallic or bitter taste in the mouth
• Specific deficits: loss of only individual taste qualities (e.g. only sweet or only bitter) — very rare

Clinically, phantogeusia in particular is problematic, because it is persistently present in the background and can massively impair quality of life. It occurs above all on certain medications, after radiotherapy in the head and neck region, with chronic dental diseases or as a rare neurological manifestation.

4. Taste disorder from colds and the sinuses

By a large margin the most common cause: acute viral respiratory infections. With colds and sinus infections, the nose and olfactory mucosa are blocked or inflamed — the retronasal smell component largely drops out, food tastes 'bland'. After the infection subsides, the sense of taste usually returns completely within 1 to 2 weeks.

Chronic sinusitis can lead to a persistent retronasal ventilation disorder and thereby to a persistently reduced taste experience. An ENT examination with nasal endoscopy and a CT of the sinuses if needed clarifies the findings. Therapy: conservative (nasal rinse, decongestant sprays, steroid sprays) or operative (functional endoscopic sinus surgery, FESS).

Allergic rhinitis (allergic rhinitis) and nasal polyps too can strongly reduce the taste experience. Here the therapy of the underlying cause belongs to the restoration of taste.

5. Post-Covid and SARS-CoV-2-related dysgeusia

With the COVID-19 pandemic, taste and smell disorders entered everyday clinical practice as a cardinal symptom. SARS-CoV-2 directly damages the supporting cells of the olfactory mucosa and secondarily the perception of taste too. In the acute phase, taste and smell disorders affect 30 to 80 per cent of those ill, depending on the virus variant.

Course: most of those affected recover completely within 1 to 4 weeks. In about 5 to 10 per cent the complaints persist longer than 6 months — one then speaks of a post-Covid dysgeusia or post-Covid anosmia. Characteristic here are not rarely parageusias and parosmias ('coffee tastes of petrol', 'meat smells of something rotten') — these can be agonising and often need many months, sometimes years, to recede.

Therapy of post-Covid taste disorder: what is effectively proven is above all olfactory training — even if the smell disorder is primarily in the foreground, the taste experience benefits too. Patients smell systematically twice a day at 4 different scents (classically: rose, eucalyptus, lemon, clove) over at least 12 weeks. With a proven zinc deficiency, zinc supplementation can be sensible. With pronounced parageusia, in individual cases medications such as gabapentin or local anaesthetics can be considered — in a specialist consultation. More under smell disorder.

6. Medications as a common cause

Over 200 medications are described with taste disorders as a side effect. A medication-related dysgeusia is therefore one of the most important and most easily remediable causes — if it is recognised:

• ACE inhibitors (captopril, enalapril, ramipril) — the classic 'metallic taste' in up to 5 per cent of users
• Antibiotics: clarithromycin, metronidazole (very typically metallic), tetracyclines, fluoroquinolones
• Chemotherapy agents: very common and pronounced taste disorders — cisplatin, carboplatin, doxorubicin, methotrexate, taxanes
• Thyroid medications: carbimazole, thiamazole, methimazole — in up to 25 per cent of users
• Lipid-lowering drugs: statins — rarely, but described
• Antidepressants and mood stabilisers: amitriptyline, lithium, carbamazepine
• Bisphosphonates for osteoporosis — above all in IV form
• Allopurinol for gout
• Penicillamine for rheumatism — a classic cause
• Levodopa and other Parkinson's medications
• PPIs (proton pump inhibitors) such as pantoprazole and omeprazole — rarely, but described
• Inhaled steroids for asthma — through oral thrush and changed saliva
• Cytostatics in oncology and radiotherapy in the head and neck region

Important: do not stop suspected medications on your own. With pronounced dysgeusia, discuss it with a doctor — often a dose reduction, a switch to a comparable substance or an accompanying therapy helps. More: Medication interactions, Taking medications correctly.

7. Zinc and other micronutrient deficiencies

Zinc deficiency is one of the most important and treatable causes of taste disorders — zinc is a central component of gustin, a key protein in the taste buds. A proven deficiency leads to reduced perception of taste and also of smell.

Risk factors for zinc deficiency: chronic gastrointestinal diseases (coeliac disease, Crohn's disease, ulcerative colitis), bariatric operations, a vegan/vegetarian diet without sufficient substitution, chronic alcohol consumption, older age with restricted absorption, long-term intake of PPIs or diuretics, severe burns, chronic liver diseases.

Diagnostics: determination of zinc in the serum (a fasting blood draw, values fluctuate over the course of the day!). A value below the reference range justifies a therapeutic trial over 8 to 12 weeks with 25–50 mg zinc/day orally. Important: take zinc 2 hours apart from iron supplements, calcium and tetracycline or fluoroquinolone antibiotics — mutual inhibition of absorption.

Further micronutrients with a connection to taste: vitamin B12 (relevant above all in vegans and older people, can also lead to a burning tongue), folic acid, iron (chronic iron deficiency anaemia). A complete micronutrient screening is worthwhile with persistent taste disorders without another recognisable cause.

8. Dental problems and oral health

Dry mouth (xerostomia) is an extremely common, often overlooked cause of a reduced taste experience. Saliva is essential to transport taste substances to the taste buds. Common causes of xerostomia: many medications (antidepressants, antihistamines, diuretics, opioids), irradiation in the head and neck region, Sjögren's syndrome, mouth breathing, older age. Lubricating mouth sprays, pilocarpine and a sufficient drinking amount can improve the taste experience.

Poor oral hygiene and dental diseases — caries, periodontitis, chronic gingivitis, oral thrush (a candida infection) — influence the taste experience. Bad breath and taste disorder too often go together. A dental restoration with professional tooth cleaning belongs to the basic diagnostics with every unclear taste disorder.

Poorly fitting dentures can cover the palate or the rear taste zones and reduce the taste experience — an adjustment by the dentist provides relief here. With burning mouth syndrome (BMS), taste disorders often occur in parallel — a specialised dental or pain-medicine assessment is sensible.

9. Neurological and systemic causes

Traumatic brain injury

One of the more common neurological causes — with falls, traffic accidents or sports injuries, the taste and above all smell nerves can be damaged. Taste and smell disorders after trauma have a rather reserved prognosis but can partly recover.

Stroke and neurodegenerative diseases

After strokes in certain brain regions, one-sided taste disorders can occur — usually combined with other neurological deficits. With Parkinson's disease and Alzheimer's dementia, taste and above all smell disorders can be early signs — sometimes years before the motor or cognitive symptoms.

Multiple sclerosis

In relapses, temporary taste and smell disorders can occur. Usually they are combined with other neurological symptoms such as visual disturbances or paralyses.

Tumours

Tumours in the head and neck region (floor-of-mouth carcinoma, tongue carcinoma, brain tumours near the taste centres) can cause one-sided or asymmetrical taste disorders — usually with further symptoms such as palpable lumps, pain, swallowing difficulties. Very important: smoking and alcohol consumption increase the risk considerably.

Systemic diseases

Internal-medicine diseases too influence the taste experience: poorly controlled diabetes with autonomic neuropathy, chronic kidney disease (a uraemic taste), liver cirrhosis, thyroid diseases, Sjögren's syndrome and other autoimmune diseases, vitamin deficiency states. A basic internal-medicine work-up belongs to the assessment with persistent complaints.

10. Taste disorder in old age

With increasing age, the perception of taste decreases physiologically — from age 60 the number of functioning taste buds sinks, saliva production declines, several medications with an effect on taste come together. Studies show that about 30 per cent of people over 70 have a relevant hypogeusia — most without a medical assessment.

These changes are not just a comfort problem: they can lead to malnutrition and weight loss, because eating brings less joy. At the same time, people often over-salt with salt and sugar — which is problematic with high blood pressure and diabetes. Geriatric co-care with targeted food selection (taste-intensive herbs, well-seasoned dishes, appealing presentation) can markedly improve quality of life.

11. When to see a doctor? (warning signs)

Have it assessed by a doctor promptly if:

• the taste disorder lasts longer than 4 weeks
• it does not come back after a respiratory infection
• accompanying symptoms such as headaches, visual disturbances, speech disorders, one-sided weakness or numbness occur
• a one-sided taste disorder or an uneven distribution across the halves of the tongue
• accompanying smell disorder, dry mouth or a burning tongue
• pronounced unpleasant phantom tastes (metallic, bitter) with distress
• a new use of a medication in a temporal connection
• palpable lumps on the neck or in the mouth, swallowing difficulties, hoarseness
• unintentional weight loss through loss of appetite
• a considerable impairment of quality of life

12. Diagnostics: what the ENT doctor and neurologist do

The diagnostics depend on the history and accompanying symptoms:

• History: onset, course, affected taste qualities, accompanying symptoms, medications, infections, smoking, alcohol
• ENT examination: nasal endoscopy, inspection of the oral cavity, throat, tongue, larynx if needed
• Taste test: taste tests with standardised taste solutions (sucrose for sweet, citric acid for sour, NaCl for salty, quinine sulphate for bitter), 'taste strips' (impregnated strips) or electrical gustometry
• Smell test: Sniffin' Sticks or smell tests — almost always in parallel, because smell and taste are clinically intertwined
• Dental examination: oral hygiene, dental status, saliva production
• Basic laboratory: full blood count, inflammation values, TSH, HbA1c, liver and kidney values, zinc, vitamin B12, folic acid, iron status
• Imaging if suspected: MRI of the skull (tumour, MS, neurological differential diagnosis), CT of the sinuses with chronic sinusitis
• Neurological assessment if a central cause is suspected

More: Preparing for a doctor's appointment, Understanding blood values.

13. Therapy: what really helps

The therapy depends on the cause — there is no single therapy for dysgeusia. The most important approaches:

Infection-associated dysgeusia

With viral respiratory infections, usually spontaneous healing within 1–2 weeks. With chronic sinusitis: nasal rinses, local steroid sprays, operative restoration if needed. With allergic rhinitis: consistent anti-allergic therapy.

Post-Covid and post-viral dysgeusia

Olfactory training over at least 12 weeks — smell at 4 different scents twice a day for 20–30 seconds. With zinc deficiency, substitution. With pronounced parageusia, possibly gabapentin or topical local anaesthetics in a specialist consultation. The course is often protracted, but in most of those affected a marked improvement occurs over the course of months to 2 years.

Medication-related dysgeusia

Identification and medical adjustment of the suspected medication — dose reduction, switch or discontinuation (always medically accompanied). With absolutely needed medications, symptomatic accompaniment with mouth care, taste modification and zinc substitution if needed.

Zinc deficiency and micronutrient deficiency

With a proven deficiency, oral substitution: zinc 25–50 mg/day over 8–12 weeks, B12 parenterally or orally with a deficiency, iron depending on the cause. Checks of the values after 8 to 12 weeks.

Dry mouth (xerostomia)

Saliva substitutes, artificial saliva, pilocarpine (with a proven Sjögren's syndrome), adjustment of medication causes, a sufficient drinking amount, sugar-free chewing gum for saliva stimulation.

Burning mouth syndrome (BMS)

A specialist consultation — therapy options: clonazepam (locally as a lozenge), gabapentin, tricyclic antidepressants in a low dose, capsaicin mouth rinses, behavioural therapy. Often protracted courses with a need for interdisciplinary care.

14. What you can do yourself

• Optimise oral hygiene: brush teeth 2x daily, tongue cleaning once a day, interdental cleaning, regular professional tooth cleaning
• Drink enough: at least 1.5–2 litres of water daily — one of the most effective measures against dry mouth
• Stimulate saliva production: sugar-free chewing gum with xylitol, lozenges, sour sweets (against dry mouth)
• Prefer taste-intensive foods — herbs (basil, parsley, coriander), spices (pepper, chilli, cumin), aromatic types of vegetable and herbal teas
• Eat with contrast — different textures and temperatures in one dish: crunchy + creamy, warm + cold — compensates for the loss of taste
• Stop smoking — demonstrably harms the taste and smell nerves and is a modifiable risk factor
• Reduce alcohol — chronic consumption damages both the sense of taste and zinc absorption
• Olfactory training with post-Covid: smell at 4 different scents 2x daily (rose, eucalyptus, lemon, clove)
• Patience: many taste disorders heal slowly over weeks to months — giving up prematurely lessens the chance of healing

How brite helps you with taste disorders

brite supports you in better understanding a taste disorder (dysgeusia) and keeping an overview of your medications.

• Intake reminder — take zinc, vitamin B12 or prescribed medications regularly: brite reminds you on time. Set up a reminder
• Interaction check — recognise a taste disorder as a medication side effect and check combinations for free — especially with ACE inhibitors, antibiotics and thyroid medications. Check now
• Health timeline — document a symptom diary with the course, affected taste qualities and accompanying symptoms over time.
• Digital medication plan — all medications clearly laid out for your GP, ENT doctor, dentist and pharmacy. To the medication plan

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