About one in every 10 Americans will suffer from the burning, gnawing abdominal pain of a peptic ulcer (in the stomach) or gastric ulcer (in the small intestine) at some point in life. Ulcers are similar to burns that form in the lining of the upper part of the GI tract. Until the mid-1980s, it was widely believed that ulcers formed as a result of stress, a genetic predisposition to excessive stomach acid secretion and poor lifestyle habits. While excessive stomach acid secretion certainly plays a role in the development of ulcers, a recent theory holds that bacterial infection is the primary cause of peptic ulcers. Other factors that may contribute to ulcer formation include excessive use of over-the-counter painkillers (such as aspirin, ibuprofen and naproxen), heavy alcohol consumption, psychological stress and smoking. With burning pain as the most common symptom, peptic ulcers affect as many as 5 million people in the U.S. alone.