Gastritis is an irritation of the stomach lining without an ulcer. Causes include excess use of alcohol, anti-inflammatory drugs (such as aspirin, ibuprofen, prednisone) and spicy foods. Peptic Ulcer is an open sore in the lining of the stomach. An infection in the stomach by H. pylori bacteria is the cause for most ulcers. This bacteria synthesize UREASE which produces ammonia that damages the gastric lining. It also neutralizes the acid pH and allows the organism to live in the stomach without being damaged by the acidity in it.