Our own research on canker sores leads us to believe that:
Primarily, different diseases are the primary causes of canker sores.
Secondly, for 8 out of 10 people, canker sores are not linked to an initial oral problem but to a metabolic imbalance in the body. It is on this imbalance 'disorder' that we have focused our research and which we have tried to understand better in order to help people suffering from canker sores.
Thirdly, the origins of this imbalance are probably and are to some extent genetic.
What causes canker sores is poorly understood. It is also unclear whether the three clinical presentations of the canker sores are manifestations of one single disease5.
There is often a genetic basis for RAS (the scientific term for recurring canker sore). A given individual has a 90% chance to have canker sores when both his parents have a history of RAS, are affected, but only 20% percent when neither parent has a history of canker sores6.
Canker sores have no link with herpes though telling the two apart can sometimes be difficult5
Canker sores are not contagious. For some time it was thought that aphthous ulcerations were due to an L-form of Streptococcus since this organism was often isolated. A more common belief is that the lesions may become secondarily infected with streptococci5.
A precipitating factor is something that help canker sores to start but it is not what causes canker sores. The following potentially precipitating factors have been studied:
Recurring aphthous stomatitis is likely to affect HIV-positive patients as well as people undergoing chemotherapy.