Dysgeusia, also known as parageusia, is a distortion of the sense of taste. Dysgeusia is also often associated with ageusia, which is the complete lack of taste, and hypogeusia, which is a 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 chemotherapy, asthma treatment with albuterol, and zinc deficiency. Liver disease, hypothyroidism, and rarely certain types of seizures can also lead to dysgeusia. 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. Signs and symptoms
The alterations in the sense of taste, usually a metallic taste, and sometimes smell are the only symptoms. Causes
Chemotherapy
A major cause of dysgeusia is chemotherapy for cancer. Chemotherapy often induces damage to the oral cavity, resulting in oral mucositis, oral infection, and salivary gland dysfunction. Oral mucositis consists of inflammation of the mouth, along with sores and ulcers in the tissues.
There is not a sufficient amount of evidence to determine whether or not zinc supplementation is able to treat dysgeusia when low zinc concentrations are not detected in the blood.A Cochrane Review in 2017 assessed the effects of different interventions for the management of taste disturbances. There was very low-quality evidence to support the role of zinc supplementation in the improvement of taste acuity and taste discrimination in patients with zinc deficiency or idiopathic taste disorders. Further research is required to improve the quality of evidence for zinc supplementation as an effective intervention for the management of dysgeusia. Zinc infusion in chemotherapy
It has been reported that approximately 68% of cancer patients undergoing chemotherapy experience disturbances in sensory perception such as dysgeusia. In a pilot study involving twelve lung cancer patients, chemotherapy drugs were infused with zinc in order to test its potential as a treatment. The results indicated that, after two weeks, no taste disturbances were reported by the patients who received the zinc-supplemented treatment while most of the patients in the control group who did not receive the zinc reported taste alterations. A multi-institutional study involving a larger sample size of 169 patients, however, indicated that zinc-infused chemotherapy did not have an effect on the development of taste disorders in cancer patients. An excess amount of zinc in the body can have negative effects on the immune system, and physicians must use caution when administering zinc to immunocompromised cancer patients.