What Causes Body Itch Without Rashes?

My son is 29, and healthy. In July he began to experience itchy throughout this body. He did not break out in hives, or has a rash. He tried Benadryl and every anti cream the MD prescribed. He went to the MD and and was given a Benadryl and steroid injection. He is still itchy to a point where he is miserable, feels like he can t comprehend, cries himself to sleep and gets very upset with me and his dad when we ask how he is feeling. He has eaten same food, no change in detergents, soaps, etc. He just went to minor emergency because he can t stand it anymore. He s beginning his first year of teaching and starts work on Monday. Can you please help me give him some relief. Please Advise!