Hi, Welcome to HCM. Many factors predispose to recurrent oral ulcers and these are few of them: 1. Broken teeth 2. Trauma 3. Stress 4. Cessation of smoking 5. Food allergy Certain foods like citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, and strawberries) can trigger an oral ulcer. I suggest multivitamin tablets twice daily for 15 days. Application of dentogel over the sores after food. If they do not reduce, you need to get in touch with a physician and get investigated for autoimmune disorders like crohn s disease, immunodeficiency disorders. Thanks.