I was actually going to ask about that. When I get a food allergy, I don't just get hives around and in my mouth. I get them at the other end too(if you catch my drift). The food goes ALL the way through! Or if it's a liquid, I can get hives around the opening of the urethra too. But if it's just my mouth, it's more likely something I inhaled or used just in my mouth like toothpaste or mouthwash. Face creams, soap, lip balm, make-up are all suspect...even shampoo. But breathing in something you are allergic to can do it too. I get the worse hives from using asthma inhalers....they not only give me asthma but give me horrible hives in my mouth, around it and my whole face swells.
Be careful with any diet you use to eliminate. Even a plain white fish can cause a lot of problems if you are sensitive to fish or the compounRAB that might be in them like lead. Had someone one here not to long ago with lead poisoning from eating too much fish. Nothing is pure anymore unless you grow it yourself. And you are still susceptible to run-off from your neigrabroador's lawn.
Start keeping a detailed journal of everything you eat and do and even the weather. Sooner or later you'll see a pattern that lines up with the presence of your symptoms. Even record stress as stress can cause hives too.
And my point about colors was not just the artificial colors but the natural coloring in all fooRAB. You can be allergic to what makes a blueberry, blue or a strawberry, red. Even what makes a lemon so tart. It doesn't have to be artificial, it can be a naturally occurring chemical like malic acid in apples or citric acid in tomatoes. You can become allergic to anything, including yourself...that is what an auto-immune disorder is.....you have become allergic to your own body and it is attacking itself.
Good luck in your search.................Jenny