The enjoyment of tastes should be one of the greatest pleasures in life. Without the sense of taste, one cannot enjoy one's food. The result would then be poor appetite, eating less and weight loss. As the elderly population in Japan increases, the number of patients suffering from taste disorder has also increased. While changes in the ability to distinguish tastes are partly associated with advancing age, they occur moreover in response to secondary influences, such as the side effects of drugs, or the effects of some diseases including periodontal disease/oral infections, nervous disorders, nutritional impairment, and endocrine disorders. Some drugs affect sensitivity to taste by directly stimulating the taste receptors, not only altering the normal transmission process and cellular functions, but also altering the salivary flow. The reduction of salivary flow strongly correlates with a decline in taste perception. In cases of taste disorder, early detection and treatment are important because the appreciation of taste is vital for overall health and long life.