Taste disorders

Summary

Taste is a complex experience. Taste receptors in the tongue, palate and throat detect qualities including sweet, sour, salty, bitter and umami; fat perception is also increasingly recognised. Texture, temperature and especially smell make an important contribution to flavour. A reduced or altered sense of taste can change eating habits, affect weight and sometimes contribute to health problems.

Taste disorders can have many causes, including inflammation, viral or fungal infections, medication, reflux, Sjögren’s syndrome and dry mouth, burns, growths, nerve injury, ear surgery, brain disease, systemic illness, pregnancy and burning-mouth symptoms. Assessment starts with a detailed medical history and ENT examination. Additional tests are sometimes needed. Treatment depends on the cause and may range from medication and dental care to, less commonly, surgery. General measures include good oral hygiene, adequate nutrition and adapting food to make eating more enjoyable.

Causes of taste disorders

Inflammation in the mouth, such as gum disease or infection of a salivary gland, can affect taste. Viral infections including herpes simplex, varicella-zoster and coxsackievirus may cause temporary loss or alteration of taste that often improves as the infection resolves. Fungal infection in the mouth can also interfere with taste receptors.

Some medicines can cause a persistent sour, bitter or metallic taste or reduce taste. Examples include certain ACE inhibitors used for high blood pressure, although many other medicines can be involved. Do not stop prescribed medication without discussing it with the prescriber. Gastro-oesophageal or throat reflux may produce a sour or bitter taste.

Severe dry mouth, including that associated with Sjögren’s syndrome or other causes of xerostomia, can impair taste. Burns and growths affecting the tongue may damage taste receptors. Injury to taste nerves, for example with facial-nerve problems or after ear surgery, can cause loss of taste on part of the tongue.

Brain injury or disease, including stroke or a brain tumour, can occasionally affect taste. Metabolic or systemic conditions such as an underactive thyroid, diabetes, and liver or kidney disease may also contribute. Taste sensitivity can change during pregnancy; some people notice greater sensitivity to bitter tastes early in pregnancy or altered preferences later on.

Assessment of a taste disorder

The clinician will ask about the nature, onset and duration of the problem and about associated symptoms such as a reduced sense of smell, mouth inflammation or reduced saliva. Medication, previous operations and radiotherapy are also relevant.

An ENT examination includes careful inspection of the mouth and, when appropriate, palpation of the tongue and neck. Because much of what people call “taste” is actually smell, a smell test may be useful. Formal taste testing is less commonly required and may assess recognition of sweet, sour, salty and bitter solutions.

Treatment

Treatment is directed at the cause. Mouth inflammation and infection may require medication or referral to a dentist or oral and maxillofacial specialist. Taste commonly improves after a viral illness resolves, while fungal infection can be treated with antifungal medication.

Taste-nerve injury after surgery may improve over time, but permanent nerve damage can leave a lasting deficit. Treating an underactive thyroid or correcting malnutrition may improve associated taste problems. Taste loss after head-and-neck radiotherapy can sometimes recover gradually. Saliva substitutes or measures that stimulate saliva may help when dry mouth is important.

If a medicine is suspected, the prescriber can review alternatives; recovery may follow a safe change or discontinuation, but some effects can last longer. When no cause is found, improvement can still occur over one or two years, although this cannot be guaranteed.

General advice

• Maintain good oral hygiene and regular dental care.
• Ensure adequate food and fluid intake, especially if reduced taste has lowered your appetite.
• Avoid compensating with excessive sugar or salt.
• Experiment with texture, temperature, herbs, spices and acidity to make food more appealing.
• Some people find carbonated drinks or a balanced combination of sweet, sour and bitter flavours helpful.
• Flavour enhancers such as monosodium glutamate may help some people, but consider dietary restrictions and professional advice.
• If your sense of smell is intact, strengthening food aromas can improve flavour perception.

Contact a doctor promptly if a taste change is sudden, one-sided, associated with neurological symptoms, a mouth or neck lump, unexplained weight loss or inability to maintain adequate nutrition.