Often when people are looking for the causes of their bad breath, they look for culprits inside the mouth, then the nose and throat. Sometimes the cause of bad breath comes from something external, most notably medications.

One of the biggest causes of bad breath is xerostomia, more commonly known as dry mouth. Many drugs have side effects that reduce of saliva. Since saliva is slightly acidic, it reduces the number of bacteria that can cause bad breath. With the saliva reduced, these bacteria reproduce much more rapidly. Saliva also oxygenates the mouth, which tends to “freshen” breath naturally.

Among the most common medications that lead to bad breath are oral antihistamines. Because they block certain receptors to the brain, the side effects can be dry mouth and bad breath. Non - sedative antihistamines such as loratidine (found in Claritin and Alavert) work very differently, and so don’t bring on the bad breath.

Many over the counter medications (including some used to fight bad breath) contain alcohol or a high amount of sugar. Alcohol, as anyone who’s ever had a hangover knows, dehydrates everywhere, including the mouth. The sugars in alcohol also help to feed the bacteria that break down sulfur in the mouth, making the mouth produce bad breath more efficiently.

While heavy use of alcohol can lead to bad breath, unfortunately, two of the common medical treatments for alcoholism also can cause bad breath. Paraldehyde, an anti-convulsive drug also used to treat alcoholism commonly produced bad breath, and its successor, Disulfuram, commonly called Antabuse, isn’t much better because of its high sulfur content.

Another popular ingredient in over the counter pain medication, especially those used to treat acid reflux, is DMSO, or dimethyl sulfate. DMSO also contains high sulfur content, and so increases the likelihood of bad breath. This is compounded for acid reflux sufferers, because acid reflux and related illnesses also contribute to bad breath.

Any medication that lists dry mouth as a side effect has the potential to lead to bad breath. These commonly include antidepressants, blood pressure medications, diuretics, narcotics, or just about any anti-anxiety medications can produce xerostomia.

With the range of medications available today, from prescription, and over the counter drugs, herbal or alternative medicines, it’s difficult to be familiar with all their side effects. The best solution is to see your doctor, and tell him or her everything you’re taking.

If you’re taking any of these drugs, the benefits of taking the medication far outweigh the drawbacks of taking the medication. One thing that helps while you’re on the medication is to increase your daily intake of water. Chewing sugar free gum or hard candies both encourage saliva flow, and so help to counteract the effects of your medication on your breath.