There are four gastrointestinal conditions that manifest symptoms in your mouth.
The first is Inflammatory Bowel Disease, attributed primarily to Crohn’s Disease, which can cause small sites of inflammation and swelling inside the lips, gums, and tissues lining the mouth. People can treat it because they usually know their diagnosis prior to the onset of these symptoms.
The second is Acid Reflux, which can dissolve tooth enamel over time. It stems from the regurgitation of very acidic stomach contents when someone has a hiatal hernia, untreated bulimia, or GERD.
The third condition I see is Jaundice, caused by increased bilirubin in the blood. It makes the attachment on the underside of the tongue turn yellow. In some cases, the back portion of the roof of the mouth can turn yellow too.
Finally, poor absorption of necessary nutrients can cause the fourth change in intraoral tissues. This occurs when bowel function is altered, either during gastric bypass surgery or bowel resection because this patient may develop an iron deficiency or have difficulty absorbing Vitamin B 12. These patients sometimes experience a burning sensation that can then expand to an inflamed or infected, bright red tongue.