Halitosis, or bad breath, is a clinical sign that can point to several things. It's possible for the bacteria that causes ulcers, H. Pylori, to cause some people to have bad breath. Bad breath is caused by excessive bacterial activity on the tongue in most cases (85%-90%), and gum disease which produces high levels of foul odors. A small percent of bad breath is related to the stomach. If oral hygiene is not the case, speak to your doctor regarding possible other causes.