The most efficient way to eliminate bad breath is to find the cause and deal with that directly. Typically, bad breath stems from bacteria growing on food that accumulates between the teeth, on the tongue and around the gums. The obvious solution is brushing your teeth twice a day, flossing between your teeth daily and brushing your tongue as well as your teeth with your toothbrush or gum scraper, a special metal or plastic instrument you use once or twice a day. Mouthwashes may help, but often don't penetrate into the crevices of the tongue.
Persistent bad breath (or a bad taste in the mouth) can be a warning sign of gum disease. A dental checkup can spot early signs of this problem, and your dentist can recommend treatment.
Insufficient secretion of saliva as a result of salivary gland problems, breathing through the mouth or taking one or more of a number of medications that make the mouth dry can also cause bad breath. The drugs that can be responsible include decongestants, diuretics and other blood pressure medications, antidepressants, antihistamines, muscle relaxants, drugs for urinary incontinence and drugs used to treat Parkinson's disease. If you take any of these regularly, ask your doctor or pharmacist to suggest an alternative.
Bad breath can also be a sign of thrush, postnasal drip, chronic bronchitis, a respiratory tract infection, diabetes, a gastrointestinal problem or liver or kidney disease. Before investigating these possible causes, see your dentist to determine whether or not your breath problem originates in your mouth.
Acidophilus is a general name for dried or liquid live cultures of lactobacillus bacteria that sour milk. They are considered "friendly" organisms in the intestinal tract. I've seen claims that these products can reduce bad breath, but I know of no scientific research to back this up. Similar products, such as Flora Balance, are unlikely to help either. Like acidophilus, they affect the colon and large intestine in the lower end of the digestive tract, while problems that cause bad breath are typically higher up (sinus problems, gum disease, oral cavity, tonsils, decaying food particles, infected teeth). Occasionally, bacterial overgrowth of the small intestine can result in bad breath. If no other cause can be found, a test for methane in the breath can determine if bacterial overgrowth is your problem.
Andrew Weil, M.D.