Hello, I read your message and understood your medical problem. Mesenteric adenitis is the inflammation of the lymph nodes of the tummy and it usually due to an infection in children. It usually goes away within a week and it is not a dangerous condition. I see your son develops episodes of diarrhea and vomiting in the morning when he eats dairy or hotdog for dinner. This is a typical scenery much more related to the food than to any infection. As the symptoms are related to dairy, a lactose intolerance is very probable in this case. Food poisoning is another condition to be considered. Remove dairy from his diet and if these episodes do not occur any more than the cause is identified. Your doctor may ask you to do a lactose tolerance test for your son to be sure for the diagnosis. In children episodes of diarrhea and vomiting have numerous causes and further investigation may be necessary for example stool examination. Hope this was helpful.