I am allergic to a wide range of inhalants, foods, medicines and molds. In fact, I was so consistent in my reactions that my allergist, the late Vincent A. Marinkovich M.D., Certified Allergist & Immunologist Clinical Professor, Stanford University, used me as a test subject for various studies. Specimens of my blood was used, among others, to develop the Mast blood test. In my case hives are caused by drug reactions and exposure to ammonia such as cleaning solutions and decoppering solvents. My suggestion is not to guess about what is going on, but to consult with an allergist as soon as possible. These things can become serious, such as when I'd hemorrhage after consuming a bowl of milk and cereal.