Extraoral halitosis in functional dyspepsia and its association with small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) and extraoral halitosis are often observed in functional dyspepsia (FD). We aimed to identify their associations for the first time. In this study, extraoral halitosis was diagnosed and assessed through the organoleptic score (OLS). Total symptom score (TSS) of FD, SIBO, gastric<i>Helicobacter pylori</i>(<i>H. pylori</i>) infection, and three exhaled volatile sulfur compounds (VSCs) (hydrogen sulfide, methyl mercaptan, and dimethyl sulfide (DMS)), were evaluated. Finally, 63 non-halitosis patients and 45 halitosis patients with extraoral halitosis were identified. Compared to non-halitosis patients, halitosis patients exhibited significantly higher TSS (86 [56, 123] vs 43 [34, 57],<i>P</i>< 0.001) and SIBO positivity rate (66.67% vs 11.11%,<i>P</i>< 0.001), but similar<i>H. pylori</i>positivity rate. The adjusted odds ratios of TSS and SIBO were 1.06 and 5.02, respectively. The area under curve of the combination of TSS and SIBO for predicting extraoral halitosis was 0.89. Positive correlations were observed between TSS and OLS (<i>r</i>= 0.64), and between TSS and exhaled DMS level (<i>r</i>= 0.86), respectively. The other two VSCs were undetectable or of little value. We conclude that: (1) Extraoral halitosis is closely associated with FD and SIBO; (2) DMS is its primary contributing VSC; (3) FD patients with SIBO as opposed to gastric<i>H. pylori</i>infection are more prone to extraoral halitosis; (4) Clinicians should be aware of SIBO in the management of extraoral halitosis in FD.