Mouth Ulcer Causes & Treatment | Muh K Chalon Ka Ilaj | Dr. Imran Zia | Dentist A mouth ulcer is a medical term for a sore in your mouth. Mouth ulcers can be painful and take a long time to heal. It can be caused by many different things including stress, injury, or infection. 1- Trauma or Injury 2- Infections 3- Oral Hygiene 4- Nutritional Deficiencies 5- Hormonal Changes | Qasim Ali Shah Foundation