The Association of Extra-oral Halitosis With Small Intestinal Bacterial Overgrowth in Inflammatory Bowel Disease

To the Editors,

We read with interest the article by Varma et al, which reported that proton pump inhibitors (PPIs) were associated with a 3-fold increased risk for enteric infection in patients with inflammatory bowel disease (IBD) but had a modest absolute risk, as demonstrated by multiplex polymerase chain reaction testing panel (GIPCR) and/or Clostridoides difficile toxin PCR.¹

Small intestinal bacterial overgrowth (SIBO) is a subtype of enteric infection, characterized by an increase in the bacterial content of the small intestine above normal values.² The primary diagnostic methods include lactulose/glucose breath tests (LBT/GBT) and jejunal bacterial culture quantification.² Furthermore, long-term use of PPIs contributes to SIBO or C. difficile and other intestinal infections.³ In addition to PPI administration, IBD itself is closely associated with SIBO, with a prevalence rate of 56% in ulcerative colitis (UC) and 32.6% in Crohn’s disease (CD).^4,5

Our specialist team is dedicated to exploring the association of halitosis with various gastrointestinal diseases. Halitosis, which is an important extraintestinal manifestation (EIM) of IBD, can have a profoundly negative impact on a patient’s quality of life (QOL).^6,7 Halitosis in IBD is categorized as intra-oral halitosis and extra-oral halitosis.⁶ Intra-oral halitosis, which is primarily caused by poor oral hygiene conditions like a thick tongue coating, emits odors directly from the mouth. In contrast, extra-oral halitosis in IBD is “blood-borne.” This condition occurs when overgrown bacteria in the small intestine produce copious amounts of malodorous volatile sulfur compounds (VSCs) including hydrogen sulfide (H₂S), methyl mercaptan (MM), and dimethyl sulfide (DMS), as well as malodorous volatile organic compounds (VOCs) such as skatole. These compounds are absorbed into the bloodstream, carried to the lungs, and exhaled out.⁶ Based on this pathogenic process, we proposed a hypothesis that SIBO in IBD might contribute to extra-oral halitosis. Our team conducted an unpublished pilot observational study using the organoleptic test (OLT) to diagnose extra-oral halitosis and the GBT to diagnose SIBO. The results showed that 59.18% (32 of 55) of the UC patients suffered from extra-oral halitosis. Of the halitosis patients, 84.38% (27 of 32) had positive SIBO, a significantly higher rate than the 21.74% (5 of 23) positive SIBO rate among non-halitosis patients (P < .001). The relative risk (RR) of positive SIBO for extra-oral halitosis was 3.88 (95% confidence interval [CI], 1.96-8.83).

In conclusion, SIBO in IBD may be a potential cause of extra-oral halitosis and must be appropriately addressed. Further randomized controlled trials (RCTs) are warranted to obtain more solid results.

Acknowledgments

We acknowledge the staff in our halitosis clinic and gastroenterology department.

Funding

This work was supported by National Natural Science Foundation of China (grant number 81900494 to Xiao Xian Qian).

Conflicts of Interest

Authors have no conflict of interest to declare.

Data Availability

The data that support the findings of this study are available upon reasonable request from the authors.

References