Taste disorders

Taste (or, more formally, gustation; adjectival form: "gustatory") is a form of direct chemoreception and is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons. In humans and many other vertebrate animals the sense of taste partners with the less direct sense of smell, in the brain's perception of flavor. In the West, experts traditionally identified four taste sensations: sweet, salty, sour, and bitter. In the Eastern hemisphere, piquance (the sensation provided by, among other things, chili peppers) and savoriness (also known as umami) have been traditionally identified as basic tastes as well. More recently, psychophysicists and neuroscientists have suggested other taste categories (fatty acid taste most prominently, as well as the sensation of metallic and water tastes, although the latter is commonly disregarded due to the phenomenon of taste adaptation.) Taste is a sensory function of the central nervous system. The receptor cells for taste in humans are found on the surface of the tongue, along the soft palate, and in the epithelium of the pharynx and epiglottis.

Common taste disorders

• ageusia (complete loss of taste)
• dysgeusia (persistent abnormal taste)
• hypergeusia

Ageusia

Ageusia is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami (the taste of monosodium glutamate). It is sometimes confused with anosmia – a loss of the sense of smell. Because the tongue can only indicate texture and differentiate between sweet, sour, bitter, salty, and umami most of what is perceived as the sense of taste is actually derived from smell. True aguesia is relatively rare compared to hypogeusia — a partial loss of taste — and dysgeusia — a distortion or alteration of taste.

Dysgeusia

Dysgeusia is the distortion of the sense of taste. Dysgeusia is also often associated with ageusia, which is the complete lack of taste, and hypogeusia, which is the decrease in taste sensitivity. 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 chemotheraphy and zinc deficiency. Different drugs could 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 of dysgeusia. These include artificial saliva, pilocarpine, zinc supplementation, alterations in drug therapy, and alpha lipoic acid.

Hypergeusia

Hypergeusia is a taste disorder where the sense is abnormally heightened.

It can be associated with a lesion of the posterior fossa and Addison's Disease; where a patient will crave for salty and sour taste due to the abnormal loss of ions with urine.