Hi.. Welcome to HEALTHCARE MAGIC.. So sorry to hear about your problem and will try my level best to resolve it to the best of my knowledge and experience.. As per your complain it seems that swelling and itching of gums after wearing dentures can be due to some sharp areas in the dentures that must be rubbing against the gums leading to gum inflammation, swelling and pain.. Secondly there is a possibility that the denture is loose and not fitting well as it can also cause improper rubbing of denture to the gums leading to the following symptoms.. Chances of allergic reaction to denture material is less probable as allergic reaction to dental material is very rarely seen.. Thrush or Oral Yeast infection is also not looking probable as per symptoms as it appears as white patches or coating over tongue and other mucosal surfaces.. I would suggest you to consult your Dentist and get evaluated and he can do a clinical evaluation and also assess your denture and if any sharp areas are present on tissue surface he can smoothen it to relieve your symptoms.. If denture us loose relining ilor rebasing can be done or a new denture can be fabricated... As of now gargle with numbing mouthwash containing Lignocaine, do warm saline gargles and do cool compresses on gums.. Hope this helps.. Regards..