I have a lot of sympathy for the level of recurrence some on here are having. I dont get anything like the frequency but I do get some particularly brutal mouth ulcers, often bigger than a 5p, when i'm extra stressed and suffering from poor sleep.
The link with sugary food is noticeable but lead to much smaller issues, likewise ill sometimes get a small ulcer or two if coming down with something.
When I was a teenager I was referred to specialist as I had a massive single ulcer in the join between tongue mouth. They were pretty dismissive, offered no special treatments beyond saying salt water would be helpful and Anbesol 15 min before eating to take the edge off. I basically still do this whenever anything kicks off, and I always have Anbesol at home in case, It hurts a lot when you put it on, but the pain fades and you get some merciful relief for a while.
My dad, grandad, uncle and sister are all similar sufferers.