A mouth sore can be a symptom of one of these 6 conditions.

Consumption of certain drugs can cause the appearance of cans in the mouth.
Deficiencies of iron, folic acid and vitamin B12 are also causing sores.
The constant presence of cans of can be associated with hereditary and genetic factors. Some people are more likely to suffer from the formation of this type of ulcer.
Weeds can occur a few days before the menstrual cycle, due to hormonal changes.