Smoking, alcohol use, gastritis, acidity, tumors of stomach and food pipe, bleeding gastric ulcer,
cancer of stomach, erosion of lining of food pipe, bleeding veins at esophageal (food pipe) sphincters etc all cause vomiting of blood. This can be fresh red if coming from a place above the stomach. It can be brown or coffee colored if coming from the stomach. Tumors/cancers of the oral cavity or mouth, pyorrhea or pus in gums and Vitamin C deficiency can cause bleeding from mouth.