Metallic Taste in the Mouth: Causes and Clinical Approach
Metallic taste is most commonly caused by medications (particularly zopiclone/eszopiclone, ethionamide, and acetylcholinesterase inhibitors), metal hypersensitivity from dental restorations, chemotherapy, and age-related changes in taste perception. 1
Medication-Induced Metallic Taste
The most frequent medication-related cause is zopiclone and eszopiclone, which produce bitter/metallic taste in 7-26% of patients, representing their most common adverse effect. 1 The risk difference compared to placebo is +0.07, with some studies showing rates as high as 26.1% versus 5.6% with placebo. 1
- Ethionamide commonly causes profound metallic taste along with nausea and vomiting, though symptoms may improve when doses are taken with food or at bedtime. 1
- Acetylcholinesterase inhibitors used for Alzheimer's disease treatment are a common cause of increased saliva production and altered taste. 2
- Women experience metallic taste from medications more frequently than men. 3
Dental and Oral Causes
Metal hypersensitivity to nickel, aluminum, vanadium, and titanium in dental or orthopedic implants can cause both local and systemic symptoms including metallic taste. 1 Dental alloy restorations can release lead and cadmium into bodily fluids, creating a confounding factor. 4
Chemotherapy-Related Metallic Taste
Chemotherapy patients frequently report "metal mouth" that overpowers and interferes with food enjoyment, adversely affecting appetite and potentially endangering recovery. 5 This affects 46% of cancer patients receiving systemic therapy, with 34% of those specifically reporting metallic taste. 3
- Patients treated with chemotherapy, concomitant radiotherapy, and targeted therapy are all at risk for this taste alteration. 3
- The etiology involves multiple mechanisms: possible phantageusia (release-of-inhibition phenomena), direct drug effects, chemotherapy-induced TRPV1 sensitization, and retronasal olfaction of lipid oxidation products. 5
Age-Related Changes
Healthy aging contributes to alterations in olfaction and gustatory sensation, with changes in mastication muscles and lower salivary flow rates exacerbating taste problems in older adults. 1 Many medications consumed by older adults further contribute to taste disturbances. 1
Systematic Clinical Assessment
When evaluating metallic taste, prioritize a systematic assessment including medication review, laboratory testing, oral examination, and psychiatric screening. 1
Key Assessment Steps:
- Conduct a thorough medication review, specifically identifying zopiclone, eszopiclone, ethionamide, acetylcholinesterase inhibitors, and chemotherapy agents. 1
- Examine for dental restorations and implants containing nickel, aluminum, vanadium, or titanium that may cause metal hypersensitivity. 1
- Evaluate for recent dental work, as sampling close in time to dental procedures should be avoided due to metal release. 4
- Assess for signs of periodontal disease, as oral and gum diseases can contribute to taste alterations. 2
- Screen for depression and anxiety, as these commonly co-occur with taste disorders. 6
Important Caveats:
- Avoid teeth brushing or oral hygiene products 1-2 hours before clinical assessment to minimize blood contamination that could falsely elevate findings. 4
- Note any recent acute infections, especially upper respiratory tract infections within the past 2 weeks, as immune markers are elevated and can affect taste. 4
- Document food consumption patterns, as acidic foods stimulate saliva production more than sugar or carbohydrate-rich foods and can exacerbate symptoms. 2, 6
Differential Considerations
Burning mouth syndrome (BMS) patients report persistently altered metallic taste or diminished taste sensations, with acidic foods causing considerable distress. 6 This represents a neuropathic disorder with altered sensory processing following small fiber neuropathic changes in the tongue. 6