Yes they tested him for allergies and only thing that showed was that he is allergic to pet dander, dust mites, grass and some type of weeds. He was acting lethargic for about two weeks prior to the trip to the er and he was cold all of the time and had headaches and didn't want to eat much. We thought he was tired from playing outside or either coming down with a cold but he never had fever so we kinda brushed it off. He woke up with a knot on his neck the size of a tennis ball so I rushed him to the er. Those were the only symptoms. Once in the hospital he started having fevers and bad night sweats. They tested and treated him for parasites they all came back negative. They have no idea what is causing his high eosinophils. His eosinophil count got up to 98,000 for two weeks and then they finally gave him the nucala shot. They keep telling us this is a serious condition and it's rare in children his age. The Dr's said they have never had a case like this before and have ran so many test on him because they can't find out what is causing it. He sees an immunologist dr a pulmonologist dr and an oncologist monthly and has labs ever other week to check his levels. I have been reading up on idiopathic hypereosinophilic syndrome but I'm still so confused and worried. We want to know what is causing this and why did it pop up out of no where.