My 3 year old son is having diarrhea (3-4 times daily) with blood containing mucus. The blood is always at the end of the bowel movement. About 4 months ago my son had this same problem, we eliminated dairy products and most juices (apple & orange) from his diet. The problem then went away in a short time (week or so). Both times my son's pediatrician has tested a stool sample for bacteria, both times the test have come back negative. The bowel movements are usually preceded by abdominal cramping. Other than cramping there are no other symptoms. He eats well, very active, no fever, growing well, etc. We have an appointment on the 10th to see a pediatric specialist. Is this IBS, allergic colitis, or ulcerative colitis? Several member's (sister & aunt) of my wife's family have been diagnosed with IBS, is IBS hereditary? Thanks.