What Causes Rashes In Chest , Ears And Neck?

We went to Doc yesterday and they said my 7year old son with Autism had a very small infection in one ear. I noticed when we got home (before starting antibiotics) that he had a itchy rash behind his ear and down chest. Now his ears are very red and hot and he is scratching them very very hard... His chest, neck, back, behind ears, and cheeks are now broken out in a very red raised rash... very itchy. It has the "sand paper" feel yet hive like as well.. Thanks...