We tend to take our sense of taste for granted—until something goes wrong. A metallic taste in the mouth is a form of dysgeusia, an abnormality of the sense of taste. There are many possible causes of having a metallic taste in your mouth, ranging from medicines to systemic disorders to environmental hazards.
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Medications are a leading cause of a metallic taste in the mouth. The types of drugs that can cause this side effect include certain drugs that treat a wide range of conditions including bacterial infection; heart and blood pressure problems; cancer; hyperthyroid; arthritis; diabetes; heartburn; glaucoma; osteoporosis; and insomnia -- among others.
Oral Health and Sinus Problems
Problems with the mouth and teeth can alter your sense of taste. Plaque buildup, gingivitis, periodontitis, tooth decay and abscesses can produce a bad taste in your mouth, which may be experienced as a metallic taste. Sinus infections and medicines or illnesses that cause dryness of the mouth, such as lichen planus and sicca syndrome, can also sometimes lead to a metallic taste. Similarly, dry mouth that accompanies the aging process may lead to taste disturbances.
Many systemic diseases can cause a metallic taste in the mouth, including cancer, hyperparathyroidism, renal failure, diabetes, Sjögren's syndrome, sarcoidosis, amyloidosis, vitamin B-12 deficiency and zinc deficiency.
Nervous System Diseases
Nervous system disorders can potentially cause taste disturbances. The problem may be located in the brain or anywhere along the peripheral nerves that control the senses of taste and smell. Because taste and smell complement one another, a disturbance in your sense of smell may be perceived as an abnormality in your sense of taste. Tumors, inflammatory diseases and autoimmune diseases affecting the central or peripheral nervous system can be associated with a metallic taste in the mouth.
The hormone fluctuations that accompany pregnancy are believed to cause the metallic taste reported by some women, especially during the first trimester.
Abnormally high levels of metals in the body, such as copper and iron, are associated with a persistent metallic taste.
Marine Food Poisoning
Eating spoiled fish—especially dark meat fish such as tuna, mackerel, bonito and mahi mahi—may cause a temporary metallic taste in the mouth. This type of food poisoning is called scombroid or histamine fish poisoning.
Allergies have been known to cause a metallic taste in the mouth. This can be due to direct local effects on taste and smell (such as a runny or stuffy nose) or the release of histamines caused by an allergic reaction.
Smoking adversely affects the taste buds, which can lead to a metallic taste in the mouth. Environmental chemicals that are inhaled over a prolonged period can also cause a metallic taste. Examples include benzene, hydrazine, gasoline, lacquers, rubber dust, chromates and cobalt.
In some cases, the cause of a metallic taste in the mouth cannot be determined. This is called idiopathic dysgeusia.