They can be triggered by a number of foods when the blood cleansing ability of the liver has become ineffective due to the presence of stones in the liver bile ducts. They also occur when intestinal congestion causes backflushing of waste particles and bile into the stomach, and from there towards the throat and mouth, often along with some hydrochloric acid). Mouth/tongue ulcers basically indicate presence of similar ones in corresponding sections of the GI tract.

Eating cooked tomatoes, vinegar, commercial salad dressings, fruit juices, particularly orange juices, peanuts, rancid nuts (most nuts go rancid quickly, except almonds, nutrasweet and other artificial sweenteners, cheese, raisins that are in cold cereals or kept together with nuts (they develop fungi), fruits that have been harvested too early (like most), junk foods that have added chemicals, colorings and preservatives in them, etc.

A hidden tooth infection can also be responsible for the sores.

With kind regards
Andreas