Dysgeusia is an abnormality in the sense of taste. The word has taken on a general meaning to include any distortion of taste—bad taste, diminished taste, or altered taste.
Related words are hypogeusia (reduced sense of taste, usually related to the tongue); hyposmia (decreased sense of smell); and parageusia (bad taste in the mouth, often used interchangeably with dysgeusia).
Mechanics of Taste
Imagine sampling chocolate ice cream. The spoonful enters your mouth, where you feel the texture. It slides over your tongue, where you sense the sweetness. You exhale slowly, letting air from your mouth up and out your nose. Along that path, chocolate flavor molecules collide with nasal sensors, sending the pleasurable response to appreciative centers in the brain. Whatever your favorite food is, the mechanics of taste are the same.
Besides sweet, the tongue can also sense sour, salty, bitter, and umami. Umami or savory is the taste of glutamate, often added to foods as MSG. The tongue has an important role in taste, but it can’t taste chocolate, or anything else other than sweet, sour, salty, bitter and umami. The nose is responsible for most of what is considered flavor.
Causes of Dysgeusia
Dysgeusia can be caused by conditions that affect the mouth, nasal passages, or brain.
- Foods and Minerals: Zinc deficiency; possibly vitamin A or thiamine deficiency
- Medications: Blood pressure medications, e.g., ACE inhibitors; certain eye drops (tears can enter the nasal passages); Metronidazole (e.g., Flagyl); Chemotherapy for cancer; certain mouthwashes (e.g., chlorhexidine [PerioGard])
- Inhaled toxins: Tobacco smoke; Formaldehyde
- Central Brain Conditions: Alzheimer's; Parkinson’s; certain strokes; Subarachnoid hemorrhage
- Endocrine Conditions: Hypothyroid; Diabetes; Addison’s
- Other conditions: Sarcoidosis (affecting neural structures); Wegener granulomatosis; Multiple sclerosis
Age also affects taste, by decreasing sensitivity to flavor molecules. This is one reason some weight loss is common in advancing age.
Impact Of Dysgeusia
Dysgeusia can affect quality of life. If your favorite food is chocolate ice cream, imagine eating tasteless chocolate ice cream, or perhaps worse, bad tasting chocolate ice cream. Eating attractive and good tasting food is an important component on life’s good-things-to-enjoy list.
More than that, however, dysgeusia can lead to decreased eating, weight loss, and weakness. These in turn can lead to increased risk of injuries from falls, and decreased immunity to infectious diseases. Or dysgeusia can lead to non-adherence to healthy diets for diabetes or heart disease, making the disease more dangerous.
The good news is that dysgeusia often is temporary. In one small study, dysgeusia disappeared within a year in two thirds of the people. (Deems, DA. 1996; Archives Otolaryngology- Head Neck Surgery)
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