Dysgeusia

Dysgeusia, also known as parageusia, is a distortion of the sense of taste. Dysgeusia is also often associated with ageusia, which is the complete lack of taste, and hypogeusia, which is a decrease in taste sensitivity.<ref>Steven K. Feske and Martin A. Samuels, Office Practice of Neurology 2nd ed. (Philadelphia: Elsevier Science, 2003) 114.</ref> An alteration in taste or smell may be a secondary process in various disease states, or it may be the primary symptom. The distortion in the sense of taste is the only symptom, and diagnosis is usually complicated since the sense of taste is tied together with other sensory systems. Common causes of dysgeusia include chemotherapy, asthma treatment with albuterol, and zinc deficiency. Liver disease, hypothyroidism, and rarely, certain types of seizures can also lead to dysgeusia. Different drugs can also be responsible for altering taste and resulting in dysgeusia. Due to the variety of causes of dysgeusia, there are many possible treatments that are effective in alleviating or terminating the symptoms. These include artificial saliva, pilocarpine, zinc supplementation, alterations in drug therapy, and alpha lipoic acid.

Signs and symptoms

The alterations in the sense of taste, usually a metallic taste, and sometimes smell are the only symptoms.<ref>Template:Cite journal</ref>

Causes

Chemotherapy

A major cause of dysgeusia is chemotherapy for cancer. Chemotherapy often induces damage to the oral cavity, resulting in oral mucositis, oral infection, and salivary gland dysfunction. Oral mucositis consists of inflammation of the mouth, along with sores and ulcers in the tissues.<ref name=Judith>Template:Cite journal</ref> Healthy individuals normally have a diverse range of microbial organisms residing in their oral cavities; however, chemotherapy can permit these typically non-pathogenic agents to cause serious infection, which may result in a decrease in saliva. In addition, patients who undergo radiation therapy also lose salivary tissues.<ref name="pmid16772071">Template:Cite journal</ref> Saliva is an important component of the taste mechanism. Saliva both interacts with and protects the taste receptors in the mouth.<ref>Template:Cite journal</ref> Saliva mediates sour and sweet tastes through bicarbonate ions and glutamate, respectively.<ref name=Speilman>Template:Cite journal</ref> The salt taste is induced when sodium chloride levels surpass the concentration in the saliva.<ref name=Speilman /> It has been reported that 50% of chemotherapy patients have had either dysgeusia or another form of taste impairment.<ref name=Judith /> Examples of chemotherapy treatments that can lead to dysgeusia are cyclophosphamide, cisplatin, vismodegib,<ref>Template:Cite web</ref> and etoposide.<ref name=Judith /> The exact mechanism of chemotherapy-induced dysgeusia is unknown.<ref name=Judith />

Taste buds

Distortions in the taste buds may give rise to dysgeusia. In a study conducted by Masahide Yasuda and Hitoshi Tomita from Nihon University of Japan, it has been observed that patients with this taste disorder have fewer microvilli than normal. In addition, the nucleus and cytoplasm of the taste bud cells have been reduced. Based on their findings, dysgeusia results from loss of microvilli and the reduction of Type III intracellular vesicles, all of which could potentially interfere with the gustatory pathway. Radiation to head and neck also results in direct destruction of taste buds, apart from effects of altered salivary output.<ref name=Masahide />

Zinc deficiency

Another primary cause of dysgeusia is zinc deficiency. While the exact role of zinc in dysgeusia is unknown, it has been cited that zinc is partly responsible for the repair and production of taste buds. Zinc somehow directly or indirectly interacts with carbonic anhydrase VI, influencing the concentration of gustin, which is linked to the production of taste buds.<ref name=Heckman/> It has also been reported that patients treated with zinc experience an elevation in calcium concentration in the saliva.<ref name=Heckman /> In order to work properly, taste buds rely on calcium receptors.<ref name=Joseph>Joseph M. Bicknell, MD and Robert V. Wiggins, MD, "Taste Disorder From Zinc Deficiency After Tonsillectomy," The Western Journal of Medicine Oct.1988: 458.</ref> Zinc "is an important cofactor for alkaline phosphatase, the most abundant enzyme in taste bud membranes; it is also a component of a parotid salivary protein important to the development and maintenance of normal taste buds".<ref name=Joseph />

Taste Modifiers

Miraculin Found in miracle berries, sweetens nonsweet food and beverages.

Gymnema sylvestre Blocks the ability to taste sweetness.

Drugs

There are also a wide variety of drugs that can trigger dysgeusia, including zopiclone,<ref>Template:Cite web</ref> H₁-antihistamines, such as azelastine and emedastine.<ref>Template:Cite journal</ref> Approximately 250 drugs affect taste, including Paxlovid, a drug used to treat COVID-19.<ref name=Samuel>Steven K. Feske and Martin A. Samuels, Office Practice of Neurology 2nd ed. (Philadelphia: Elsevier Science, 2003) 119.</ref> Some describe so-called "Paxlovid mouth" as like a "mouthful of dirty pennies and rotten soymilk", according to the Wall Street Journal.<ref>Template:Cite news</ref>

The sodium channels linked to taste receptors can be inhibited by amiloride, and the creation of new taste buds and saliva can be impeded by antiproliferative drugs.<ref name=Samuel /> Saliva can have traces of the drug, giving rise to a metallic flavor in the mouth; examples include lithium carbonate and tetracyclines.<ref name=Samuel /> Drugs containing sulfhydryl groups, including penicillamine and captopril, may react with zinc and cause deficiency.<ref name=Joseph /> Metronidazole and chlorhexidine have been found to interact with metal ions that associate with the cell membrane.<ref>Template:Cite journal</ref> Drugs that act by blocking the renin–angiotensin–aldosterone system, for example by antagonizing the angiotensin II receptor (as eprosartan does), have been linked to dysgeusia.<ref>Template:Cite journal</ref> There are few case reports claiming calcium channel blockers like Amlodipine also cause dysgeusia by blocking calcium sensitive taste buds.<ref>Template:Cite journal</ref>

Pregnancy

Changes in hormone levels during pregnancy, such as estrogen, can affect the sense of taste.<ref name=whatToExpect>Template:Cite web</ref> A study found that 93 percent of pregnant women reported some change in taste during pregnancy.<ref name=whatToExpect />

Miscellaneous causes

Xerostomia, also known as dry mouth syndrome, can precipitate dysgeusia because normal salivary flow and concentration are necessary for taste. Injury to the glossopharyngeal nerve can result in dysgeusia. In addition, damage done to the pons, thalamus, and midbrain, all of which compose the gustatory pathway, can be potential factors.<ref name=RK>R. K. Mal and M. A. Birchall, "Dysgeusia related to urinary obstruction from benign prostatic disease: a case control and qualitative study," European Archives of Oto-Rhino Laryngology 24 Aug. 2005:178.</ref> In a case study, 22% of patients who were experiencing a bladder obstruction were also experiencing dysgeusia. Dysgeusia was eliminated in 100% of these patients once the obstruction was removed.<ref name=RK /> Although it is uncertain what the relationship between bladder relief and dysgeusia entails, it has been observed that the areas responsible for urinary system and taste in the pons and cerebral cortex in the brain are close in proximity.<ref name=RK />

Dysgeusia can be a symptom of head and neck cancer. In this case it often present together with having dry mouth.<ref name=":11">Template:Cite journal</ref>

Dysgeusia often occurs for unknown reasons. A wide range of miscellaneous factors may contribute to this taste disorder, such as gastric reflux, lead poisoning, and diabetes mellitus.<ref name=Norman>Norman M. Mann, MD, "Management of Smell and Taste Problems," Cleveland Clinic Journal of Medicine Apr. 2002: 334.</ref> A minority of pine nuts can apparently cause taste disturbances, for reasons which are not entirely proven.

Certain pesticides can have damaging effects on the taste buds and nerves in the mouth. These pesticides include organochloride compounds and carbamate pesticides.<ref name=Norman />

Damage to the peripheral nerves, along with injury to the chorda tympani branch of the facial nerve, also cause dysgeusia.<ref name=Norman /> A surgical risk for laryngoscopy and tonsillectomy include dysgeusia.<ref name=Norman /> Patients with burning mouth syndrome, primarily menopausal women, often have dysgeusia as well.<ref>Giuseppe Lauria, Alessandra Majorana, Monica borgna, Raffaella Lombardi, Paola Penza, Alessandro padovani, and Pierluigi Sapelli, "Trigeminal small-fiber sensory neuropathy causes burning mouth syndrome," Pain 11 Mar. 2005: 332, 336.</ref>

Normal function

The sense of taste is based on the detection of chemicals by specialized taste cells in the mouth. The mouth, throat, larynx, and esophagus all have taste buds, which are replaced every ten days. Each taste bud contains receptor cells.<ref name=Norman /> Afferent nerves make contact with the receptor cells at the base of the taste bud.<ref>Template:Cite journal</ref> A single taste bud is innervated by several afferent nerves, while a single efferent fiber innervates several taste buds.<ref>Template:Cite journal</ref> Fungiform papillae are present on the anterior portion of the tongue while circumvallate papillae and foliate papillae are found on the posterior portion of the tongue. The salivary glands are responsible for keeping the taste buds moist with saliva.<ref>Template:Cite journal</ref>

A single taste bud is composed of four types of cells, and each taste bud has between 30 and 80 cells. Type I cells are thinly shaped, usually in the periphery of other cells. They also contain high amounts of chromatin. Type II cells have prominent nuclei and nucleoli with much less chromatin than Type I cells. Type III cells have multiple mitochondria and large vesicles. Type I, II, and III cells also contain synapses. Type IV cells are normally rooted at the posterior end of the taste bud. Every cell in the taste bud forms microvilli at the ends.<ref name=Masahide>Template:Cite journal</ref>

Diagnosis

In general, gustatory disorders are challenging to diagnose and evaluate. Because gustatory functions are tied to the sense of smell, the somatosensory system, and the perception of pain (such as in tasting spicy foods), it is difficult to examine sensations mediated through an individual system.<ref>Template:Cite journal</ref> In addition, gustatory dysfunction is rare when compared to olfactory disorders.<ref name=Hummel>Hummel T, Knecht M. Smell and taste disorders. In: Calhoun KH, ed. Expert Guide to Otolaryngology. Philadelphia, Pa: American College of Physicians; 2001:650-664.</ref>

Diagnosis of dysgeusia begins with the patient being questioned about salivation, swallowing, chewing, oral pain, previous ear infections (possibly indicated by hearing or balance problems), oral hygiene, and stomach problems.<ref name=Schiffman>Template:Cite journal</ref> The initial history assessment also considers the possibility of accompanying diseases such as diabetes mellitus, hypothyroidism, or cancer.<ref name=Schiffman /> A clinical examination is conducted and includes an inspection of the tongue and the oral cavity. Furthermore, the ear canal is inspected, as lesions of the chorda tympani have a predilection for this site.<ref name=Schiffman />

Gustatory testing

In order to further classify the extent of dysgeusia and clinically measure the sense of taste, gustatory testing may be performed. Gustatory testing is performed either as a whole-mouth procedure or as a regional test. In both techniques, natural or electrical stimuli can be used. In regional testing, 20 to 50 μL of liquid stimulus is presented to the anterior and posterior tongue using a pipette, soaked filter-paper disks, or cotton swabs.<ref name=Hummel /> In whole mouth testing, small quantities (2-10 mL) of solution are administered, and the patient is asked to swish the solution around in the mouth.<ref name=Hummel />

Threshold tests for sucrose (sweet), citric acid (sour), sodium chloride (salty), and quinine or caffeine (bitter) are frequently performed with natural stimuli. One of the most frequently used techniques is the "three-drop test".<ref name=Ahne>Template:Cite journal</ref> In this test, three drops of liquid are presented to the subject. One of the drops is of the taste stimulus, and the other two drops are pure water.<ref name=Ahne /> Threshold is defined as the concentration at which the patient identifies the taste correctly three times in a row.<ref name=Ahne />

Suprathreshold tests, which provide intensities of taste stimuli above threshold levels, are used to assess the patient's ability to differentiate between different intensities of taste and to estimate the magnitude of suprathreshold loss of taste. From these tests, ratings of pleasantness can be obtained using either the direct scaling or magnitude matching method and may be of value in the diagnosis of dysgeusia. Direct scaling tests show the ability to discriminate among different intensities of stimuli and whether a stimulus of one quality (sweet) is stronger or weaker than a stimulus of another quality (sour).<ref name=Seiden>Seiden, Allen M., "Taste and Smell Disorders (Rhinology & Sinusology)," Thieme Publishing Group Aug. 2000: 153.</ref> Direct scaling cannot be used to determine if a taste stimulus is being perceived at abnormal levels. In this case, magnitude matching is used, in which a patient is asked to rate the intensities of taste stimuli and stimuli of another sensory system, such as the loudness of a tone, on a similar scale.<ref name=Seiden /> For example, the Connecticut Chemosensory Clinical Research Center asks patients to rate the intensities of NaCl, sucrose, citric acid and quinine-HCl stimuli, and the loudness of 1000 Hz tones.<ref name=Seiden />

Other tests include identification or discrimination of common taste substances. Topical anesthesia of the tongue has been reported to be of use in the diagnosis of dysgeusia as well, since it has been shown to relieve the symptoms of dysgeusia temporarily.<ref name=Hummel /> In addition to techniques based on the administration of chemicals to the tongue, electrogustometry is frequently used. It is based on the induction of gustatory sensations by means of an anodal electrical direct current. Patients usually report sour or metallic sensations similar to those associated with touching both poles of a live battery to the tongue.<ref>Template:Cite journal</ref> Although electrogustometry is widely used, there seems to be a poor correlation between electrically and chemically induced sensations.<ref>Template:Cite journal</ref>

Diagnostic tools

Certain diagnostic tools can also be used to help determine the extent of dysgeusia. Electrophysiological tests and simple reflex tests may be applied to identify abnormalities in the nerve-to-brainstem pathways. For example, the blink reflex may be used to evaluate the integrity of the trigeminal nerve–pontine brainstem–facial nerve pathway, which may play a role in gustatory function.<ref>Template:Cite journal</ref>

Structural imaging is routinely used to investigate lesions in the taste pathway. Magnetic resonance imaging allows direct visualization of the cranial nerves.<ref name=Lell>Template:Cite journal</ref> Furthermore, it provides significant information about the type and cause of a lesion.<ref name=Lell /> Analysis of mucosal blood flow in the oral cavity in combination with the assessment of autonomous cardiovascular factors appears to be useful in the diagnosis of autonomic nervous system disorders in burning mouth syndrome and in patients with inborn disorders, both of which are associated with gustatory dysfunction.<ref>Template:Cite journal</ref> Cell cultures may also be used.<ref name="Doyle Premathilake Yao Mazucanti 2023 pp. 1193–1246">Template:Cite journal</ref>

In addition, the analysis of saliva should be performed, as it constitutes the environment of taste receptors, including transport of tastes to the receptor and protection of the taste receptor.<ref name=Matsuo>Template:Cite journal</ref> Typical clinical investigations involve sialometry and sialochemistry.<ref name=Matsuo /> Studies have shown that electron micrographs of taste receptors obtained from saliva samples indicate pathological changes in the taste buds of patients with dysgeusia and other gustatory disorders.<ref>Template:Cite journal</ref>

Treatments

Artificial saliva and pilocarpine

Template:Main Because medications have been linked to approximately 22% to 28% of all cases of dysgeusia, researching a treatment for this particular cause has been important.<ref name=Giudice>Template:Cite journal</ref> Xerostomia, or a decrease in saliva flow, can be a side effect of many drugs, which, in turn, can lead to the development of taste disturbances such as dysgeusia.<ref name=Giudice /> Patients can lessen the effects of xerostomia with breath mints, sugarless gum, or lozenges; or physicians can increase saliva flow with artificial saliva or oral pilocarpine.<ref name=Giudice /> Artificial saliva mimics the characteristics of natural saliva by lubricating and protecting the mouth, but does not provide any digestive or enzymatic benefits.<ref name=Preetha>Preetha, A. and R. Banerjee, "Comparison of Artificial Saliva Substitutes, Trends in Biomaterials and Artificial Organs, Jan. 2005: 179.</ref> Pilocarpine is a cholinergic drug, meaning it has the same effects as the neurotransmitter acetylcholine. Acetylcholine has the function of stimulating the salivary glands to actively produce saliva.<ref name="Medications and Drugs">"Medications and Drugs," 6 May 2004, 25 Oct. 2009, <http://www.medicinenet.com/pilocarpine/article.htm></ref> The increase in saliva flow is effective in improving the movement of tastants to the taste buds.<ref name=Giudice />

Zinc deficiency

Zinc supplementation

Zinc Gluconate.

Approximately one half of drug-related taste distortions are caused by a zinc deficiency.<ref name=Giudice /> Many medications are known to chelate, or bind, zinc, preventing the element from functioning properly.<ref name=Giudice /> Due to the causal relationship of insufficient zinc levels to taste disorders, research has been conducted to test the efficacy of zinc supplementation as a possible treatment for dysgeusia. In a randomized clinical trial, fifty patients with idiopathic dysgeusia were given either zinc or a lactose placebo.<ref name=Heckman>Template:Cite journal</ref> The patients prescribed the zinc reported experiencing improved taste function and less severe symptoms compared to the control group, suggesting that zinc may be a beneficial treatment.<ref name=Heckman /> The efficacy of zinc, however, has been ambiguous in the past. In a second study, 94% of patients who were provided with zinc supplementation did not experience any improvement in their condition.<ref name=Giudice /> This ambiguity is most likely due to small sample sizes and the wide range of causes of dysgeusia.<ref name=Heckman /> A recommended daily oral dose of 25–100 mg, as zinc gluconate, appears to be an effective treatment for taste dysfunction provided that there are low levels of zinc in the blood serum.<ref name=Heyneman>Template:Cite journal</ref> There is not a sufficient amount of evidence to determine whether or not zinc supplementation is able to treat dysgeusia when low zinc concentrations are not detected in the blood.<ref name=Heyneman />

A Cochrane Review in 2017 assessed the effects of different interventions for the management of taste disturbances. There was very low-quality evidence to support the role of zinc supplementation in the improvement of taste acuity and taste discrimination in patients with zinc deficiency or idiopathic taste disorders. Further research is required to improve the quality of evidence for zinc supplementation as an effective intervention for the management of dysgeusia.<ref>Template:Cite journal</ref>

Zinc infusion in chemotherapy

It has been reported that approximately 68% of cancer patients undergoing chemotherapy experience disturbances in sensory perception such as dysgeusia.<ref name=Hong>Hong, Jae Hee, et al., "Taste and Odor Abnormalities in Cancer Patients," The Journal of Supportive Oncology, Mar./Apr. 2009: 59-64.</ref> In a pilot study involving twelve lung cancer patients, chemotherapy drugs were infused with zinc in order to test its potential as a treatment.<ref name=Yamagata>Template:Cite journal</ref> The results indicated that, after two weeks, no taste disturbances were reported by the patients who received the zinc-supplemented treatment while most of the patients in the control group who did not receive the zinc reported taste alterations.<ref name=Yamagata /> A multi-institutional study involving a larger sample size of 169 patients, however, indicated that zinc-infused chemotherapy did not have an effect on the development of taste disorders in cancer patients.<ref name=Hong /> An excess amount of zinc in the body can have negative effects on the immune system, and physicians must use caution when administering zinc to immunocompromised cancer patients.<ref name=Hong /> Because taste disorders can have detrimental effects on a patient's quality of life, more research needs to be conducted concerning possible treatments such as zinc supplementation.<ref name=Halyard>Template:Cite journal</ref>

Altering drug therapy

Eprosartan.

The effects of drug-related dysgeusia can often be reversed by stopping the patient's regimen of the taste altering medication.<ref name=Bromley>Bromley, Steven M., "Smell and Taste Disorders: A Primary Care Approach," American Family Physician 15 Jan. 2000, 23 Oct. 2009 <http://www.aafp.org/afp/20000115/427.html Template:Webarchive></ref> In one case, a forty-eight-year-old woman who had hypertension was being treated with valsartan.<ref name=Castells>Castells, Xavier, et al., "Drug Points: Dysgeusia and Burning Mouth Syndrome by Eprosartan," British Medical Journal, 30 Nov. 2002: 1277.</ref> Due to this drug's inability to treat her condition, she began taking a regimen of eprosartan, an angiotensin II receptor antagonist.<ref name=Castells /> Within three weeks, she began experiencing a metallic taste and a burning sensation in her mouth that ceased when she stopped taking the medication.<ref name=Castells /> When she began taking eprosartan on a second occasion, her dysgeusia returned.<ref name=Castells /> In a second case, a fifty-nine-year-old man was prescribed amlodipine in order to treat his hypertension.<ref name=Sadasivam>Template:Cite journal</ref> After eight years of taking the drug, he developed a loss of taste sensation and numbness in his tongue.<ref name=Sadasivam /> When he ran out of his medication, he decided not to obtain a refill and stopped taking amlodipine.<ref name=Sadasivam /> Following this self-removal, he reported experiencing a return of his taste sensation.<ref name=Sadasivam /> Once he refilled his prescription and began taking amlodipine a second time, his taste disturbance reoccurred.<ref name=Sadasivam /> These two cases suggest that there is an association between these drugs and taste disorders. This link is supported by the "de-challenge" and "re-challenge" that took place in both instances.<ref name=Sadasivam /> It appears that drug-induced dysgeusia can be alleviated by reducing the drug's dose or by substituting a second drug from the same class.<ref name=Giudice />

Alpha lipoic acid

Alpha lipoic acid (ALA) is an antioxidant that is made naturally by human cells.<ref name=UMMC>University of Maryland Medical Center, "Alpha-lipoic Acid," 26 Oct. 2009</ref> It can also be administered in capsules or can be found in foods such as red meat, organ meats, and yeast.<ref name=UMMC /> Like other antioxidants, it functions by ridding the body of harmful free radicals that can cause damage to tissues and organs.<ref name=UMMC /> It has an important role in the Krebs cycle as a coenzyme leading to the production of antioxidants, intracellular glutathione, and nerve-growth factors.<ref name=Femiano>Template:Cite journal</ref> Animal research has also uncovered the ability of ALA to improve nerve conduction velocity.<ref name=Femiano /> Because flavors are perceived by differences in electric potential through specific nerves innervating the tongue, idiopathic dysgeusia may be a form of a neuropathy.<ref name=Femiano /> ALA has proven to be an effective treatment for burning mouth syndrome, spurring studies in its potential to treat dysgeusia.<ref name=Femiano /> In a study of forty-four patients diagnosed with the disorder, one half was treated with the drug for two months, while the other half, the control group, was given a placebo for two months, followed by a two-month treatment of ALA.<ref name=Femiano /> The results showed that 91% of the group initially treated with ALA reported an improvement in their condition compared to only 36% of the control group.<ref name=Femiano /> After the control group was treated with ALA, 72% reported an improvement.<ref name=Femiano /> This study suggests that ALA may be a potential treatment for patients, and supports that full double blind randomized studies should be performed.<ref name=Femiano />

Managing dysgeusia

In addition to the aforementioned treatments, there are also many management approaches that can alleviate the symptoms of dysgeusia. These include using non-metallic silverware, avoiding metallic- or bitter-tasting foods, increasing the consumption of foods high in protein, flavoring foods with spices and seasonings, serving foods cold in order to reduce any unpleasant taste or odor, frequently brushing one's teeth and utilizing mouthwash, or using sialogogues such as sugar-free gum or sour-tasting drops that stimulate the production of saliva.<ref name=Hong /> When taste is impeded, the food experience can also be improved through means other than taste, such as texture, aroma, temperature, and color.<ref name=Bromley />

Psychological impacts

People with dysgeusia are also forced to manage the impact that the disorder has on their quality of life. An altered sense of taste has effects on food choice and intake, and can lead to weight loss, malnutrition, impaired immunity, and a decline in health.<ref name=Bromley /> Patients diagnosed with dysgeusia must use caution when adding sugar and salt to food, and must be sure not to overcompensate for their lack of taste with excess amounts.<ref name=Bromley /> Since the elderly are often on multiple medications, they are at risk for taste disturbances, increasing the chances of developing depression, loss of appetite, and extreme weight loss.<ref name=Padala>Template:Cite journal</ref> This is cause for evaluation and management of their dysgeusia. In patients undergoing chemotherapy, taste distortions can often be severe, and make compliance with cancer treatment difficult.<ref name=Yamagata /> Other problems that may arise include anorexia, and behavioral changes that can be misinterpreted as psychiatric delusions regarding food.<ref name=Bicknell>Template:Cite journal</ref> Symptoms including paranoia, amnesia, cerebellar malfunction, and lethargy can also manifest when undergoing histidine treatment.<ref name=Bicknell />

Future research

Every year, more than 200,000 individuals see their physicians concerning chemosensory problems, and many more taste disturbances are never reported.<ref name=NIDOCD>National Institute on Deafness and Other Communication Disorders, "Taste Disorders," 25 June 2008, 23 Oct. 2009 <http://www.nidcd.nih.gov/health/smelltaste/taste.asp Template:Webarchive></ref> Due to the large number of persons affected by taste disorders, basic and clinical research are both receiving support at different institutions and chemosensory research centers across the United States.<ref name=NIDOCD /> These taste and smell clinics are focusing their research on better understanding the mechanisms involved in gustatory function and taste disorders such as dysgeusia. For example, the National Institute on Deafness and Other Communication Disorders is looking into the mechanisms underlying the key receptors on taste cells, and applying this knowledge to the future of medications and artificial food products.<ref name=NIDOCD /> Meanwhile, the Taste and Smell Clinic at the University of Connecticut Health Center is integrating behavioral, neurophysiological, and genetic studies involving stimulus concentrations and intensities, in order to better understand taste function.<ref name=UCHC>The University of Connecticut Health Center, "Taste and Smell: Research," 26 Oct. 2009 <http://www.uchc.edu/uconntasteandsmell/research/index.html></ref>

See also

• Anosmia
• Parosmia

External links

• Dysgeusia at NIH