One of my relatives has bad breath. Common causes, including dry oral cavity, poor dental health, dirty tongue coating, tonsil stones, are ruled out. We now suspect that H. pylori is the culprit.

He experiences stomachache sometimes, and is going to have a H. pylori breath test. Also, saliva samples taken nearer to oesophagus have a stronger smell, suggesting certain relation to stomach/lungs problems.

However, even the test result is positive, H. pylori might not be the actual cause. It is well known that (in our city) nearly one third of the population is infected by this bacteria, but often no symptoms can be observed.

So, I want to make a primary test before seeking advice from professionals.

How does H. pylori-caused halitosis smell like? (please be descriptive and use simile)

Some Google results suggest that the breath smells like volatile sulphur compound. However this is strongly disagreed by some articles. A few articles suggested a smell of urine, but did not give any evidence.

Thanks in advance.

  • Have you made an attempt to find the answer to this? It's readily available with a google search, which means the question isn't a good fit for the site. At least some degree of prior research is required here.
    – Carey Gregory
    Dec 30, 2018 at 21:47
  • @CareyGregory I did a search but nothing comes up. What keywords did you search?
    – Szeto
    Dec 31, 2018 at 1:07
  • 2
    I'm not the downvoter. I simply asked you what research you've done. That's a requirement here, so it's a reasonable question. Your comment above seems to indicate you've done some, so show it to us. Show us what you found and why it doesn't answer your question.
    – Carey Gregory
    Dec 31, 2018 at 6:53
  • 1
    We also have a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified, regardless of the reader's background. See this list of reliable sources. If you still have trouble with this, feel free to visit the help center or Medical Sciences Meta. Unreferenced claims can lead to answers being deleted. Dec 31, 2018 at 10:48
  • 2
    @Szeto, I strongly suggest to include the links to the sources that say: "However this is strongly disagreed by some articles." It can really help if we know who exactly says what exactly.
    – Jan
    Dec 31, 2018 at 11:06

2 Answers 2



  1. Individuals with H. pylori infection of the stomach can have increased amounts of the following substances in the breath:

  2. The variety of the substances comes from different strains of H. pylori in different individuals and, I assume, from different foods consumed.

  3. According to this 2005 review (Table 3), hydrogen nitrate with choking odor seems to be most specific, but not likely diagnostic, for H. pylori. Isobutane, 2-butanone and ethyl acetate smell like ketones in a low-carb diet or uncontrolled diabetes. Sulfide and cyanide smell can appear in various other infections.

  4. The mentioned breath odors are not anatomic-specific and may arise not only from the stomach (H. pylori) but also from the mouth (parodontosis), throat (tonsil stones), or lungs (atelectasis).

  5. Symptoms, like upper abdominal bloating and excessive belching after meals, can help in diagnosis of H. pylori.


Gastrointestinal diseases and halitosis: association of gastric Helicobacter pylori infection (PUbMed, 2002):

The levels of hydrogen sulphide and dimethyl sulphide in mouth air were also significantly higher in the [H pylori] positive patients...

Determination of volatile organic compounds in human breath for Helicobacter pylori detection by SPME-GC/MS (PubMed, 2011):

isobutane, 2-butanone and ethyl acetate were detected in the breath of persons with H. pylori in the stomach...

H. pylori infection increases levels of exhaled nitrate (PubMed, 2005):

...in H. pylori-infected patients, levels of exhaled hydrogen nitrate and hydrogen cyanide are found to be significantly elevated.

Clinical Application of Volatile Organic Compound Analysis for Detecting Infectious Diseases (PUbMed, 2013):

This review again mentions isobutane, 2-butanone, ethyl acetate, HCN and hydrogen nitrate in the breath of H pylori infected patients, but HCN is also detectable in exhaled-breath samples of P. aeruginosa-infected individuals.


It seems that H. pylori-associated gastritis is accompanied by an increased level of exhaled nitric oxide...

According to this study, H. pylori was shown to produce hydrogen sulfide and methyl mercaptan...


Here is an interesting article. “Summary: Bacteria that cause stomach ulcers and cancer could also be giving us bad breath, according to research published in the Journal of Medical Microbiology. For the first time, scientists have found Helicobacter pylori living in the mouths of people who are not showing signs of stomach disease.” (2008).

“"Although the presence of H. pylori in the mouth does not directly cause bad breath, it is associated with periodontal disease, which does cause bad breath," said Dr. Suzuki. "We now need to look into the relationship between H. pylori in the mouth and in the stomach. We hope to discover the role of the mouth in transmitting H. pylori stomach infections in the near future." https://www.sciencedaily.com/releases/2008/11/081123222846.htm

This would be H. Pylori infection of just the mouth, presumably, or at least not showing “signs” of stomach disease. Bottom line: this odor would be from gum disease caused or accelerated by H. Pylori.

So this is another route by which H. Pylori may contribute to bad breath.

No word on how it smells. Just bad.

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