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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.