Normally, gastric juices are secreted in the presence of food. Stress and smoking can also cause the stomach lining to secrete gastric juices. In the absence of food, the acidic juices erode the lining of the stomach, leaving an open sore that may bleed. This open sore is called an ulcer. Recent research has shown, however, that a bacterium, Helicobacter pylori, may be a major factor in ulcer formation. The use of antibiotics to kill the bacteria has proved quite helpful in treating many patients with ulcers.