Mouth ulcers are caused by many reasons, such as daily habits and diseases. 1. Daily habits, usually often smoke and drink, eat too hot and spicy food, often stay up late, irregular work and rest time, usually do not pay attention to oral hygiene and other reasons may cause mouth ulcers. 2. Diseases, patients with mouth ulcers may also be due to other diseases, such as gingivitis, periodontitis, gastric ulcers, gastritis, Crohn’s disease and so on. Many reasons may cause mouth ulcers, usually need to pay extra attention, if it is caused by disease, it is best to immediately consult a doctor for examination and treatment, to avoid aggravation of the condition, not conducive to the rapid recovery of the body.