Dehydration and toothbrush irritation are two more possible causes, at least according to webmd. I think we'd better wait for an expert, to answer this one.
when searching it pulls up alot for swollen gums, tongue, and glands...could you be a little bit more exact as to what part of the mouth your trying to get info on?
Does your mouth get swollen in the morning and gets better during the afternoon or at night? If yes, I think it is an allergy, especially if it is itching.
Use Blistex. You can get them from your local pharmacy.