Is it possible the canola oil can cause inflammation of the gums and or allergic reaction in the mouth?

Unlikely. In theory anything we eat or drink could cause gum inflammation due to an allergic response, but not likely. I have not heard anything specific about canola oil and would bet that your gum inflammation has more to do with your daily oral hygiene and how long it's been since you had a professional cleaning.
Anything is possible. I have never heard of a canola oil allergy, but since it is a natural substance an allergy is very possible? The gum inflammation is a possible side effect of being allergic. Best advice...Use another oil to cook with or use in your recipes.