If it's a food allergy, you can determine what food is causing the bad reactions by systematically eliminating certain foods from your diet for a few days and observing your body's reaction. Processed Sugar is a natural fermentation ingrediant. If you eat too much of it, your digestion slows down and it turns your stomach into a methane producing factory. By eliminating sugar from my toothpaste and alcohol from my oral rinse this I was able to eliminate my bad breath completely...

Good luck!