Also called: Taste Disorder
Andrew M. Sicklick, D.D.S.
Dysgeusia is the medical term for an altered, distorted or reduced ability to taste.
Specific types of taste disorders include hypogeusia (a reduced ability to taste) and ageusia (an inability to detect taste). A persistent bad taste in the mouth (parageusia) is sometimes used interchangeably with dysgeusia.
Taste buds in the mouth can detect five basic taste sensations: sweet, sour, salty, bitter and umami (savory). Umami refers to glutamate, (such as monosodium glutamate or MSG), which is found in food products such as chicken broth, meat extracts and some cheeses. For more complex tastes, the sense of smell is required. Many taste disorders are actually associated with an impaired sense of smell, which can occur due to colds or other upper respiratory infections. Often, people do not discover they have a smell disorder until they notice a problem with taste.
More than 200,000 people seek help for a taste or smell disorder every year, according to the National Institutes of Health. The actual incidence of these disorders is estimated to be in the millions because a large number of people do not seek help for the condition. Taste disorders can affect a person’s quality of life. It can lead to a decreased appetite, poor nutrition and the inability to identify potentially harmful foods or beverages.
Taste disorders can have many different causes. Various illnesses (e.g., colds, strep throat), lifestyle habits (e.g., smoking), irritants (e.g., insecticides, certain prescription mouthwash) and other factors (e.g., medications) can contribute to dysgeusia.
Patients are urged to contact their physician or dentist if they have a taste disorder that lasts two weeks or longer. A thorough medical history may be taken, including questions about symptoms, current medications and medical conditions, recent illnesses, and whether the patient’s sense of smell is affected.
The oral cavity may be inspected for any signs of infection, tooth decay or any other potential causes of dysgeusia. In some cases, x-rays may be taken. Tests that measure the extent of a person’s sense of taste or smell may be performed. If no underlying medical or dental condition is identified, the patient may be referred to a facility that specializes in taste and smell disorders.
Treatment of dysgeusia depends on its cause. Typically, treating the underlying condition will also eliminate the patient’s dysgeusia. The prognosis for patients is generally excellent when the cause of dysgeusia can be identified and treated. However, long-term recovery is more complicated when the source of dysgeusia cannot be identified or when dysgeusia results from an untreatable condition.
A taste disorder (dysgeusia) is a condition in which patients experience a distorted sense of taste or reduction in their ability to taste. Distortion may include sensing a taste that is not present in the mouth, or misidentifying a taste (e.g., pleasant-tasting foods now taste awful). Taste impairment may range from a slight decrease in a person’s ability to identify tastes (hypogeusia) to the inability to taste anything (ageusia).
The sense of taste begins in the mouth. A person is born with approximately 10,000 taste buds, most of which are located on or around the tiny bumps (papillae) of the tongue. Taste buds are also located on the soft palate, pharynx (upper portion of the throat), larynx (voice box), epiglottis (flap that covers the airway) and the first part of the esophagus.
Each taste bud contains anywhere from 50 to 100 taste cells. Each of these cells responds best to one of five basic taste sensations:
- Sweet (e.g., sugar)
- Sour (e.g., lemon juice)
- Bitter (e.g., aspirin)
- Umami (sometimes spelled umame) or “savory” (e.g., monosodium glutamate [MSG], which is found in products such as chicken broth, meat extracts and some cheeses)
When stimulated, a taste cell sends a nerve impulse to the brain, where a certain taste is identified and sensed. New taste cells are constantly being produced by the body, replacing existing taste cells every 10 days throughout a person’s life. Thus, if taste cells are destroyed by burning the mouth with a hot liquid, any consequent taste disorder is usually temporary, until new taste cells are produced.
When something interferes with these processes, dysgeusia results. Various illnesses, lifestyle habits, irritants and other factors can contribute to dysgeusia. A taste disorder persists for varying lengths of time depending on its cause. It is considered temporary when related to short-term factors such as upper respiratory infections or certain medications. On the other hand, dysgeusia caused by untreatable conditions such as some types of nerve damage may be permanent.
A person’s sense of smell helps identify more complex tastes. Special cells in the olfactory receptorsof the nose send messages to the brain about a particular taste. Most of a person’s taste sensations are dependent on the sense of smell. Sometimes patients who believe they are experiencing a taste disorder are actually experiencing a dysfunction of their sense of smell (dysosmia).
More than 200,000 people seek help for a taste or smell disorder every year, according to the National Institutes of Health. The actual incidence of these disorders is estimated to be in the millions because a large number of people do not seek help for the condition.
Taste disorders can affect a patient’s quality of life. Dysgeusia can lead to a reduced desire to eat, which can result in depression and poor nutrition. It can lead to an increased use of salt or sugar in an attempt to add taste to food, which can result in medical complications. In addition, a reduced ability to taste can prevent a person from being able to identify spoiled or otherwise harmful food or beverages (e.g., those products to which a person may be allergic).
Patients are urged to call a physician or dentist if they have a change in their sense of taste that lasts for two weeks or more. If no underlying medical or dental condition is identified, patients may be referred to a facility that specializes in taste and smell disorders.
Types and differences of dysgeusia
Dysgeusia is commonly used to refer to any type of distortion or reduced ability to taste. If the cause of the condition is unknown, it is called idiopathic dysgeusia.
Specific taste disorders include:
- Hypogeusia. Reduced ability to taste. This may be a temporary condition or it may persist. This is a common type of taste disorder.
- Ageusia. Inability to detect taste. This may apply to just one of the basic taste sensations (e.g., total loss of ability to taste anything bitter), or it may involve all (e.g., anything consumed has no detectable taste). Most often, this is a temporary condition that resolves once its cause (e.g., upper respiratory infection) goes away or is treated. True (permanent) ageusia is rare and involves unidentified or untreatable causes (e.g., nerve damage) .
- Parageusia. A persistent bad taste in the mouth or altered sense of taste. The taste is commonly described as metallic, salty, foul or rotten. This can be a debilitating type of taste disorder. It is usually a temporary condition that can have many different causes, including poor dental hygiene and many dental conditions (e.g., abscess, periodontal disease). Alternatively, the taste of foods may change. For example, a formerly pleasant-tasting food may become unpleasant. Parageusia most often appears later in life. This term is sometimes used interchangeably with dysgeusia.
Risk factors and causes of dysgeusia
Aging can contribute to a taste disorder, or dysgeusia, as the number of taste buds tends to diminish with age. There are also numerous other causes. Frequently, a distorted or reduced sense of taste is caused by a loss of smell, often due to a cold, flu or other type of upper respiratory infection.
Dysgeusia can result from many oral conditions, such as:
- Periodontal (gum) disease
- Mouth sores
- Tooth decay
- Oral abscess
- Trauma (e.g., burning the tongue)
- Salivary gland infections
- Burning mouth syndrome
- Glossitis (inflammation of the tongue)
Certain oral surgeries (e.g., wisdom teeth extractions) can also temporarily affect the sense of taste. Dentures and other oral appliances can alter the sense of taste, as can mouth rinses that contain chlorhexidine.
Lifestyle factors such as smoking (particularly pipe smoking) can cause persistent dysgeusia. Additional causes of dysgeusia include many prescription and over-the-counter medications that cause dry mouth (xerostomia). These medications include:
- Cardiovascular agents (e.g., antihypertensives)
- Chemotherapy drugs
- Thyroid medications
- Anti-anxiety medication
- NSAIDS(nonsteroidal anti-inflammatory drugs)
- Respiratory inhalants
- Nicotine skin patches
Dry mouth is also a frequent symptom of many conditions, including Sjogren’s syndrome, metabolic and thyroid disease (e.g., diabetes). Other potential causes of dysgeusia include:
- Vitamin or mineral deficiencies (e.g., vitamin B3, vitamin B12, zinc)
- Neurological disorders (e.g., Bell’s palsy, multiple sclerosis)
- Neurodegenerative diseases (e.g., Parkinson’s disease, Alzheimer’s disease)
- Cancers of the head and neck, and radiation treatments to these areas
- Lichen planus
- Exposure to certain toxins (e.g., insecticides, solvents)
- Migraine headache
- Liver or kidney problems
Signs and symptoms of dysgeusia
Symptoms of a taste disorder, or dysgeusia, are the distorted taste sensation itself or a noticeable decrease in a patient’s ability to taste. Distorted taste includes a metallic taste in the mouth when nothing is there, and previously enjoyed food suddenly tasting bad.
Taste disorders may also involve a reduced ability to taste. This can apply to one or more of the basic taste sensations (e.g., sweet, sour, bitter, salty, umami/savory), and can range from a slight reduction in tasting ability to complete taste loss.
A distorted or reduced ability to smell (dysosmia) often accompanies dysgeusia. Not more than five basic taste sensations can be identified by the sense of taste alone (sweet, sour, salty, bitter and umami [savory]). In order to identify more complex tastes, a sense of smell is necessary. Thus, the first time many patients become aware of a problem with their sense of smell is when they notice problems with their ability to taste.
Diagnosis methods for dysgeusia
In diagnosing a taste disorder, or dysgeusia, a physician or dentist will compile a thorough medical history and may perform a complete physical examination and/or dental examination.
Patients may be asked about their symptoms, including the type of taste distortion or change that has occurred and when it began. Patients may also be asked about their current medications, conditions or diseases, any recent illnesses, and whether the patient’s sense of smell is impaired. Additional symptoms (e.g., appetite) as well as any possible aggravating factors (e.g., whether a patient smokes) or alleviating factors may also be discussed.
The patient’s oral cavity will be inspected to look for signs of tooth decay, periodontal (gum) disease, infection, dry mouth or any other potential causes of dysgeusia. Sometimes x-rays, specifically computed axial tomography (CAT scans) or magnetic resonance imaging (MRI) of the head, may be taken.
Tests may be performed that measure the extent of a patient’s sense of taste or smell. Taste tests may involve sip-spit-rinse exercises or direct application of chemicals to areas of the tongue. In either case, the patient is asked to identify the taste involved. Smell tests involve identifying various types of smells on scratch-and-sniff cards.
The physician, dentist or other healthcare provider will attempt to identify the underlying cause of a patient’s dysgeusia. How symptoms of dysgeusia begin can help indicate the underlying cause. For instance, a sudden loss of taste may be due to trauma or a severe upper respiratory infection. For dysgeusia that occurs off and on, an allergy or exposure to chemicals may be the cause.
However, pinpointing an underlying cause is not always possible, which can make the condition difficult to treat.
Treatment and prevention of dysgeusia
Treatment of a taste disorder, or dysgeusia, depends on its cause. Typically, treating the underlying condition will also eliminate the patient’s dysgeusia. For example, dysgeusia caused by an upper respiratory infection will go away once the infection (e.g., cold, flu) has resolved. Dysgeusia caused by certain medications may disappear once use of those medications has been stopped. Smokers may regain their sense of taste once they quit smoking.
Some people have reported that zinc lozenges (available over-the-counter) help reduce the severity of taste disorders, although studies have not confirmed this. In fact, some dentists have found that lozenges that include zinc may lead to a taste disorder.
The prognosis for patients is generally excellent when the cause of the disorder is identified and treatable. However, long-term recovery is more complicated when the source of dysgeusia cannot be identified, or when dysgeusia results from a permanent untreatable condition, such as some forms of nerve damage.
For the most part, dysgeusia cannot be prevented. However, quitting smoking, practicing good oral hygiene, having regular dental examinations and treating sinus problems all can contribute to reducing the likelihood of dysgeusia.
Questions for your doctor regarding dysgeusia
Preparing questions in advance can help patients to have more meaningful discussions with their dentists regarding their treatment options. The following questions related to dysgeusia may be helpful:
- At what point should I see a dentist or physician about my taste disorder?
- How will you diagnose my dysgeusia?
- How should I prepare for smell or taste tests?
- What is the likely cause of my dysgeusia?
- Is my sense of smell also impaired?
- What are my treatment options? Are there any side effects of these treatments?
- How long will it be before my sense of taste improves?
- What happens if the source of my dysgeusia cannot be identified?
- If my dysgeusia is permanent, are there things I can do to improve my quality of taste?
- What can I do to prevent taste disorders in the future?