what can cause a mouth ulcer
Common causes of mouth ulcers. The most common causes of mouth ulcers are related to disturbances of the mouth and include: 1  Bacterial infections. 2  Canker sores. 3  Dietary deficiencies, such as lack of vitamin B-12, zinc, folate (folic acid), or iron. 4  Emotional stress. 5  Food allergies. 6  Nutritional deficiency. 7  Spicy foods.
Other less common viral and bacterial infections may cause mouth ulcers, but this is rare. Mouth ulcers can be caused by anaemia and occasionally by other blood disorders, and some skin or gastrointestinal diseases. Sometimes the mouth ulcers are the only sign of an underlying disease.