Have you been tested for food allergies? I love nuts but I am allergic to them. Brazil nuts can send me to the emergency room but hazelnuts and almonds just make my mouth, throat & ears itch, and I have to take Benadryl. I've never had mouth ulcers but the itching in the mouth and throat sound like an allergic reaction to me.
I visited several websites and they all said that food allergies can cause mouth ulcers as well.