These people may feel tired and weak. If the bleeding is heavy, blood will appear in vomit or stool. Stool containing blood appears tarry or black. Until recent times doctors believed lifestyle factors such as stress and diet caused ulcers. This is now thought unlikely, although some lifestyle factors, such as smoking and drinking alcohol and caffeine are still suspected of causing problems.
Physical stress is also a factor.
For example, people with injuries such as severe burns and people undergoing major surgery often require rigorous treatment to prevent ulcers and ulcer complications. Scientists later discovered that an imbalance of the digestive fluids hydrochloric acid and pepsin could also cause ulceration. Both substances are produced by the stomach, and are essential to help break down food in the first stages of the digestive process. However, they may also attack the delicate lining of the stomach and duodenum, particularly if the stomach's natural defence mechanisms break down. Normally the stomach lining produces a mucus shield.