SCIENCE

What's the stink? The true causes of bad breath

Betty Zou, Ph D.

Ah, bad breath—the bane of romantics and interviewees everywhere. For most people, it’s a temporary nuisance that pops up every now and then after a particularly garlicky meal or a long night’s slumber and goes away in a few hours. For others, though, it can be a frequent and persistent problem with detrimental effects on mental health and social interactions.

It’s hard to find precise data on just how many people are affected by halitosis, the medical term for bad breath. That’s because there are no standard methods or criteria for diagnosing the condition and large cultural variations exist in what is considered stinky. Estimates range widely from 2% in Sweden to 28% in China to roughly 50% in the U.S.

Approximately 80-90% of halitosis cases originate within the oral cavity with bacteria being the most common culprit. These bacteria breakdown dead cells and trapped food in the various nooks and crannies of your mouth and as they do so, they produce chemicals that vaporize into the unpleasant scents associated with bad breath. Chief among these are volatile sulfur compounds (VSCs), which can smell like rotten eggs or cabbage.

Like many bacteria-associated ailments, it is likely the interactions of a microbial community—as opposed to the presence or absence of a single bacterial species—that determines whether or not a person has bad breath and how severe it is. There are, however, conditions that can exacerbate halitosis by shifting the balance of the oral microbial community towards these malodorous microbes. For example, a dry mouth is often associated with bad breath because the decreased saliva flow fails to clear away food and bacteria from the oral cavity. Medications that cause dry mouth as a side effect can also indirectly lead to bad breath by creating an environment where VSC-producing bacteria flourish.

Non-oral causes of bad breath account for roughly 8% of halitosis cases. These include infections in the ears, nose and throat region or the respiratory tract. During a sinus infection, for example, mucus drips down from your nose into the back of your throat where it gets converted by bacteria into putrid gases. Gastrointestinal disorders have also been shown to cause bad breath. Patients with gastroesophageal reflux disease have been shown to have higher levels of VSCs in their breath as a result of damage to the stomach lining caused by constant acid reflux. The bacteria Helicobacter pylori, which causes gastric and peptic ulcers,can also produce VSCs which may explain why infection with this microbe is associated with halitosis.

Metabolic disorders can also be behind bad breath. In these cases, the foul compounds in your exhalation is often a byproduct of some metabolic misstep—one nutrient not being broken down properly or too much of another being produced.

And finally, let’s not forget the foods and drinks that can sour your breath. Garlic, onions and spiced foods may be the most obvious items that come to mind but alcohol, coffee and tobacco are just as likely to give you a temporary case of halitosis. The good news is that diet-induced bad breath usually resolves on its own in a few hours.

Common remedies like mints, mouthwashes and chewing gum can mask bad breath but do little to address the underlying causes. pH balanced drinks like qii can help fight bad breath at its source by creating an oral environment that favours beneficial bacteria over the odor-producing microbes. More importantly, regular flossing and brushing remove stinky bacteria and the food they depend on, keeping your VSC production to a minimum. Gently cleaning your tongue can also be helpful since the back of the tongue is one of the major reservoirs of microbes in the mouth. With good oral hygiene practices, you can keep bad breath at bay and breathe easy.

Betty Zou, Ph D.

Scientist turned science writer and communicator. I turn complex scientific concepts and studies into clear and engaging content for diverse lay audiences. Previous work include blog posts, news articles and releases, patient and customer profiles, feature length stories, donor reports and marketing materials. My areas of expertise are molecular biology, microbiology and microbiome-related topics but I have also written extensively about other health and medicine topics such as cancer, cardiology and trauma.

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