10 surprising things that give you bad breath

iStockIf you have halitosis, you might be surprised by the cause.
  • High-protein diets can cause your breath to smell.
  • Peanut butter has a lot of sugar, which bacteria love to eat.
  • Diabetes and the keto diet can both give you “acetone breath.”
  • Visit INSIDER.com for more stories.

Bad breath, or halitosis, is an unpleasant condition that we’ve all experienced from time to time. But it’s not just the tuna sandwich or garlic bread you ate for lunch that’s to blame. Myriad items can cause our breath to stink, from protein-rich foods to the keto diet.

To find out which foods and health conditions cause bad breath and why, INSIDER talked to Dr. Adam Harwood, a New York-based endodontist, Mary Lynn Bosma, global director of clinical research and medical affairs for oral healthcare at Johnson & Johnson, and Dr. Seth Schwartz, an ear, nose, and throat doctor at Virginia Mason Medical Center in Seattle, Washington.

Here are 10 surprising things that can give you bad breath.


High-protein diets can cause bad breath.

PixabayBacteria on our tongues break down proteins and can cause bad-smelling gases.

High-protein diets can cause bad breath. If you eat a lot of protein-rich foods, “you’ll have a foul taste or foul smell” in your mouth, Harwood told INSIDER.

Further, as Bosma explained, the tongue is a relatively large organ lined with indentations and irregularities. So it’s easy for bacteria to grow and for food debris particles to be captured.

In turn, bacteria break down proteins and emit malodorous gases.

“Some of the main gases that are given off are hydrogen sulfide, which you might recognise as the smell of rotten eggs, and methyl mercaptan, which is the smell of cabbage,” she said.


Dry mouth could be the reason for your bad breath.

girl-think-position/ShutterstockSaliva is actually very helpful for keeping your mouth clean.

Dry mouth, a condition in which the mouth’s salivary glands do not produce enough saliva to wet the mouth, could be the reason for your bad breath.

It can be caused by medication side effects, ageing, or other health conditions (such as diabetes, stroke, or autoimmune diseases) as well as by dehydration, the use of tobacco products, and nerve damage.

When there’s a lack of saliva, your mouth isn’t as clean, Bosma noted.

“[Saliva] moves things around the mouth, so it’s very, very helpful for having a cleaner mouth,” she said.


Citrus fruits have a lot of sugar, which bacteria in your mouth love to eat.

Boontoom Sae-Kor/ShutterstockSugars cause acids in the mouth and can lead to decay and possibly infections.

It’s not just candy bars and sweets that are full of sugar.

“Some citrus fruits cause [bad breath] because bacteria naturally in your mouth love to chow down on that,” Harwood said. “Those bacteria love to eat sugar and those sugars cause acid and those acids are going to cause decay and possibly infections.”


Peanut butter can also give you bad breath due to its sugar content.

White bear studio/ShutterstockPeanut butter may taste savoury, but it’s high in sugar content.

You may be tempted to eat peanut butter by the spoonful, but the creamy, nutty paste could be the reason why your breath smells.

“People love peanut butter but unfortunately that’s got lots of sugar in it,” Harwood said. Many brands have at least three to four grams of sugar per two-tablespoon serving. Varieties flavored with honey or chocolate could pack an even higher sugar content.


Food that collects in the pits of the tonsils can cause bad breath.

oneinchpunch/ShutterstockDebris and food can accumulate in the crevices of your tonsils.

Our tonsils have naturally occurring crevices or pockets known as crypts. However, debris such as food and mucus can accumulate inside these crevices to detrimental effect. Tonsil stones might form, accompanied by bad breath, chronic sore throat, and other symptoms.

“Sometimes the tonsils, which have deep pits within them, can collect food or food debris and that can be sometimes a cause of bad breath that doesn’t go away easily,” Schwartz told INSIDER.


Nasal issues such as crusting and bacterial infections can affect our breath.

Sarah Schmalbruch/INSIDERChronic bacterial infections in the nose can also develop bad breath.

Schwartz said that people who have crusting in the nasal cavity or chronic bacterial infections in the nose can also develop bad breath.


Chronic acid reflux can cause our breath to smell.

iStockAcid reflux is when stomach contents like acid and undigested food flow back up the esophagus.

Those who have chronic acid reflux (aka gastroesophageal reflux disease) can experience bad breath when stomach contents like acid and undigested food flow backward into the esophagus.

According to Healthline, this condition is caused by “a faulty or relaxed lower esophageal sphincter (LES),” a muscle that creates a barrier between the esophagus and the stomach.

Chronic reflux could also be caused by a hiatal hernia.


Diabetes and the ketogenic diet can cause “acetone breath.”

Like the keto diet, diabetes could also be the culprit behind “acetone breath” – breath that smells like nail polish remover. Acetone is one of the ketones (chemicals produced in the liver) that your body creates as you burn fat for energy.

“Diabetes is known to cause ketosis and ketones don’t smell very good,” Harwood said, adding that if someone is diabetic, they may also smell overly sweet due to the high levels of glucose in their blood.


Drinking alcohol kills the good bacteria in your mouth.

Georges Gobet/ AFP/ Getty ImagesHeavy drinkers had higher concentrations of certain types of bad bacteria in their mouths, one study said.

It’s not unusual to reek after a night spent drinking, but it’s not just our body odor that might stink. Drinking can also take a toll on how our breath smells because it messes with the balance of “good” and “bad” oral bacteria.

A study published in the journal Microbiome in 2018 found that heavy drinkers had higher concentrations of Actinomyces, Leptotrichia, Cardiobacterium, and Neisseria (all types of bad bacteria) in their mouths. The results were based on mouthwash samples taken from 1,044 US adults.


While coffee dehydrates the mouth, it’s likely the milk in your latte that’s to blame for bad breath.

Joe Raedle/Getty Images

If you’ve ever walked into a meeting only to realise you have coffee breath from your morning caffeine fix, you’re not alone. But it’s not just the java that’s to blame.

Researchers at Tel Aviv University in Israel found that coffee could actually neutralise breath. They learned that when saliva and coffee were mixed together, it yielded an innocuous odor rather than a pungent scent.

“We think that coffee, which has a dehydrating effect on the mouth, can ferment into bad breath when mixed with substances such as milk,” Mel Rosenberg, a breath specialist involved with the study, told CNN.

Milk and other dairy products are known to cause bad breath because they contain amino acids that generate sulphur when introduced to the mouth’s anaerobic bacteria.

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