Ask the doctors: Halitosis and metallic taste in mouth are common, usually benign

Dear Doctor: My husband has had very bad breath for several months, and lately he says he has a metallic taste in his mouth. Can you tell us what might be the cause?

Dear Reader: Bad breath is a fairly common occurrence, as is a metallic taste in the mouth. The cause of these is usually something benign, such as a lapse in oral hygiene. However, each can be a sign of a more serious condition, so it’s worthwhile to figure out what’s going on.

Let’s start with bad breath, or halitosis. A frequent cause is the presence of bacteria that live on the surface of the tongue, below the gumline and in the throat. These tiny organisms, which feed on the food particles left behind when we eat, emit an array of stinky gasses as a byproduct of their digestion. Two compounds in particular contribute to foul-smelling breath. They are hydrogen sulfide, which smells like rotten eggs, and methyl mercaptan, which smells like putrid cabbage.

Some foods that we eat, such as onions and garlic, can also contribute to bad breath. Additional common causes for unpleasant breath include the poor dental hygiene that we mentioned earlier; an infection in the mouth, teeth or gums; the use of tobacco products; or interactions with certain medications or multivitamins. Saliva plays an important role in keeping the oral cavity clean, and a condition known as dry mouth, or xerostomia, can lead to bad breath. Chronic acid reflux, sometimes referred to as gastroesophageal reflux disease, or GERD, is also associated with unpleasant odors in the mouth.

When it comes to the reasons for a metallic taste in the mouth, there’s a bit of crossover with halitosis. Poor brushing habits, certain foods and an oral infection can play a role. So can pregnancy, cancer treatments like chemotherapy and radiation therapy, and environmental exposure. Some medications may cause a metallic taste, as can multivitamins containing zinc or copper. People who follow low-carb diets often report developing a persistent metallic taste, a side effect of their bodies being in ketosis.

However, the complaint is also associated with several more serious conditions. The perception of unusual flavors can occur in certain cancers when tumor growth affects the complex cellular pathways involved in taste and smell. They can also occur in diabetes, as a result of alterations to glucose metabolism. Kidney disease, liver disease and some metabolic disorders, which are marked by a buildup of waste products, can cause both bad breath and changes to taste. Taste abnormalities are also often seen in people with dementia, due to disease-related changes in the brain.

Since both the bad breath and the metallic taste are somewhat recent changes, we think it would be a good idea for your husband to see his dentist. A thorough checkup will reveal any tooth decay, gum disease or infection. If nothing turns up and you’re still worried, consider a visit to your primary care physician, who can help identify any underlying medical problems that require attention.