Vomiting blood may be caused by:

1. Acute liver failure
2. Aspirin
3. Benign tumors of the stomach or esophagus
4. Cirrhosis (scarring of the liver)
5. Defects in gastrointestinal tract blood vessels
6. Dieulafoy's lesion (an artery that protrudes through the stomach wall)
7. Duodenitis, which is inflammation of the top part of the small intestine.
8. Esophageal cancer
9. Esophageal varices (enlarged veins in the esophagus)
10. Esophagitis (inflammation of the esophagus)
11. Gastric erosions (breakdown of tissue lining the stomach) due to H. pylori, nonsteroidal anti-inflammatory medications (NSAIDs) or other medications
12. Gastric varices (enlarged veins in the stomach) due to liver failure or portal hypertension
13. Gastritis (inflammation of the stomach lining)
14. Gastropathy (bleeding due to dilated blood vessels in the stomach lining)
15. Mallory-Weiss tear (tear in the esophagus associated with pressure caused by vomiting or coughing)
16. Nonsteroidal anti-inflammatory drugs
17. Pancreatic cancer
18. Pancreatitis
19. Peptic ulcer
20. Portal hypertension (high blood pressure in the portal vein)
21. Prolonged or vigorous vomiting
22. Stomach cancer

In infants and young children, vomiting blood may also result from:

1. Birth defects
2. Blood-clotting disorders
3. Milk allergy
4. Swallowed blood, such as from the nose or from the mother during birth
5. Swallowed object
6. Vitamin K deficiency