Causes of mouth ulcers.

• Emotional stress.
  
• Local trauma in the form of ill-fitting dentures or a sharp tooth.
  
• Allergy to local applications like toothpaste.
  
• Vitamin deficiency, especially B-complex, folic acid.
  
• In females, sometime in association with menstrual cycle.
  
• Hereditary, familial tendencies are also seen.
  
• Smoking.
  
• Poor oral hygiene such as not brushing teeth regularly.
  
• Alcohol.
  
• Spicy food.
  
• Drugs like antibiotics.
  
• Low immunity in any illness from TB to AIDS.
  
• Infectious origin like some bacteria or virus.
  
• Tartar in tooth surface.