[devy]

I've noticed the same causes and correlation. Canker sores' formal name is aphthous stomatitis. But whether it is an autoimmune disease is debatable. As noted in [1]:

"Despite this preferred theory of immuno-dysregulation held by most researchers,[7] aphthous stomatitis behaves dissimilarly to autoimmune diseases in many regards. "

[1]: http://en.wikipedia.org/wiki/Aphthous_stomatitis