There are several types of taste disorders depending on how the sense of taste is affected. People who have taste disorders usually lose their ability to taste or can no longer perceive taste in the same way.
The most common taste complaint is "phantom taste perception" -- tasting something when nothing is in the mouth. Some people have hypogeusia, or the reduced ability to taste. This disorder is usually temporary.
True taste disorders are rare. Most changes in the perception of food flavor result from the loss of smell. Other people can't detect taste at all, which is called ageusia. This type of taste disorder can be caused by head trauma; some surgical procedures, such as middle ear surgery or extraction of the third molar; radiation therapy; and viral infections.
More often, people with taste disorders experience a specific ageusia of one or more of the five taste categories: sweet, sour, bitter, salty, and umami, or savory. Your doctor may refer you to an otolaryngologist, a specialist in diseases of the ear, nose, and throat. After conducting a complete medical history and physical examination, your doctor may run special tests to find out what type of taste disorder you have and how serious it is.
Some tests are designed to measure the lowest concentration of a substance that a person can detect or recognize. Your doctor may ask your elderly mother or father to compare the tastes of different substances or to note how the intensity of a taste grows when a substances concentration is increased.
Scientists have developed taste tests in which the patient responds to different concentrations of a substance. This may involve a simple "sip, spit, and rinse" test or the application of a substance directly to your tongue using an eye dropper. By using these tests, your doctor can determine if your aging mom or dad has a true taste disorder and what type it is. If your doctor suspects that nerves in your parent's mouth or head may be affected, he or she may order an X-ray, usually a CAT scan, to look further into the head and neck area.