Their are variety of causes which can lead to mouth ulcers, finding the causative factor often helps in planning the treatment course.
Injury - badly fitting dentures or a graze from a harsh toothbrush, chewing hard foods, etc may cause injury resulting into ulcers.
Stress or anxiety is said to trigger aphthous mouth ulcers in some people. When a person is stressed body releases some chemical that affects the overall health, triggering ulcers in the mouth as well. Due to this people who are under constant stress and anxiety are prone to get recurrent mouth ulcers.
Having nutritional defficiencies like vitamin B12, iron and folic acid can lead to mouth ulcers and affects overall general health. Nutritional supplements helps in such cases to an extent but simultaneously internal medicines for correcting the sensitivity is required.
Hormonal imbalance- Some women find that mouth ulcer occur just before their period. In some women, the ulcers only develop after the menopause.
Stopping smoking - some people find they develop ulcers only after stopping smoking. That does not mean that person should start smoking again, homeopathic medicines can help in this regards.
Mouth ulcers run in some families. So, a genetic factor may play a part in some cases. Also mouth ulcers can result after some kind of food allergies.
Some medications, such as Nicorandil, ibuprofen(or any other anti-inflammatory medicine), oral nicotine therapy. Certain tablets which are supposed to be swallowed as a whole, when left to dissolve in the mouth, if kept to dissolve against a gum such as Aspirin. Alendronate, taken to treat osteoporosis, can also cause mouth ulcers if it is not taken according to the instructions.street drugs such as cocaine.
Mouth ulcers are more common in people with certain conditions - for example, Crohn's disease, coeliac disease, HIV infection and Behçet's disease. However, these ulcers are not the aphthous type.