Gastric erosion occurs when the mucous membrane lining the stomach becomes inflamed. Some drugs, as tablets, can irritate this mucous membrane, especially drugs taken for arthritis and muscular disorders, steroids, and aspirin. A gastric erosion may also occur because of emotional stress, or as a side effect of burns or stomach injuries.
There is basically one symptom of gastric erosion: bleeding from the area where the stomach lesion is. Bowel movements may contain blood. Vomit may be bloody as well, but a gastric erosion may not cause vomiting. Blood may be black because it will be partially digested. Loss of blood may cause one to develop anemia.
Anemia and other problems related to blood loss may occur. Sometimes a person with a gastric erosion will experience severe bleeding all at once; here red (bloody) vomiting may occur, and/or black bowel movements.
"Gastric Erosion." Encyclopædia Britannica, Micropaedia. Encyclopædia Britannica Inc., 1998 ed.