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The most common true taste complaint is phantom taste perceptions. Additionally, testing may demonstrate a reduced ability to taste sweet, sour, bitter, salty, and umami, which is called hypogeusia. Some people can detect no tastes, called ageusia. True taste loss is rare; perceived loss usually reflects a smell loss, which is often confused with a taste loss.
In other disorders of the chemical senses, the system may misread and or distort an odor, a taste, or a flavor. Or a person may detect a foul taste from a substance that is normally pleasant tasting.
The extent of a chemosensory disorder can be determined by measuring the lowest concentration of a chemical that a person can detect or recognize. A patient may also be asked to compare the tastes of different chemicals or to note how the intensity of a taste grows when a chemical's concentration is increased.
Scientists have developed taste testing in which the patient responds to different chemical concentrations. This may involve a simple "sip, spit, and rinse" test, or chemicals may be applied directly to specific areas of the tongue.
Some people are born with chemosensory disorders, but most develop them after an injury or illness. Upper respiratory infections are blamed for some chemosensory losses, and injury to the head can also cause taste problems.
Loss of taste can also be caused by exposure to certain chemicals such as insecticides and by some medicines. Taste disorders may result from oral health problems and some surgeries (e.g. third molar extraction and middle ear surgery). Many patients who receive radiation therapy for cancers of the head and neck develop chemosensory disorders.
If a certain medication is the cause of a taste disorder, stopping or changing the medicine may help eliminate the problem. Some patients, notably those with respiratory infections or allergies, regain their sense of taste when the illness resolves. Often the correction of a general medical problem can also correct the loss of taste. Occasionally, recovery of the chemosenses occurs spontaneously.