Diagnosis of Canker Sores:

Canker sores are very common and easy to recognize. Occasional canker sores merit self care only.

Most doctors recommend that patients who have continual or frequently recurring bouts of canker sores undergo blood and allergy tests to determine if their sores are caused by a nutritional deficiency, an allergy, or some other correctable cause.

Large or persistent ulcers may be due to drug allergies, acute herpes simplex, or certain digestive diseases.