Recurring canker sores (aphthous ulcer), all systems of medicine tried, but nothing works. any ideas?

Depends on cause: Aphthous stomatitis involving the common canker sore can occur in up to 15% of americans, and may involve some bacteria like staph epidermidis. However, similar-appearing aphthous ulcers can be seen with herpes, crohn's disease, and other systemic disorders, if you have multiple aphthous ulcers or frequently recurring ones please have the lesions checked out.

Prevention: The reaction of people to acidic foods is very variable. Some people are just more susceptible to reactions to acidic foods and drinks, like orange juice, pineapple juice, fruits, tomatoes, and others. Stress and anxiety also create problems sometimes. As far as i know, prevention is difficult except for keeping track of what you eat/drink and when you get the sores. Second opinion?!