What Causes Frequent Stomach Aches And Unexplained Bruises All Over The Body?

My son is 12 years old and has a great many stomach aches (usually every day), diarrhea almost every day and a general feeling of unwellness all of the time. He has missed a great deal of school during the last year because of this and we are at our wit s end to help him. He has been checked for Celiac s, Krohn s and we have a visit to a allergy specialist coming up. We have also noticed that he has been developing bruises all over his body lately. He has assured us that no one is bullying him and he cannot even figure out where or when he gets them. These things may have nothing in common, but as I have said, we are desperate to find something for him. We did removed dairy from his diet for a while and that seemed to help somewhat. In fact, he gets a stomach ache almost immediately after a glass of milk or ice cream. But even removing dairy has not made that big of a difference. Any advice?