<<Disclaimer: Verify this information before applying it to your situation.>> My five year old son also has developed hives. When we took him to the doctor, we were told that he probably has some allergy to something he had eaten. He was diagnosed with Celiac Sprue 1 1/2 years ago and we THINK we have him on a gluten-free diet. He only started developing hives after having a flu vaccine. We had the flu vaccine given to him because he is also diabetic so they kept pushing the idea on us. He has gotten much better, however, but for about 4 months he was miserable. Maybe another opinion by the medical profession before going thru all of the tests would put your minds at ease. I'll be thinking of you. Pat W.