Suggest Treatment For Severe Itching Skin Rashes All Over The Body

I have a 28 year old son that has developed a skin rash that we thought looked like chicken pox but they have not blistered in the three days he has had them. He has no fever to speak of till today and it is only at 100 degrees and he has cold chills today. He does not feel bad but itches. He has developed these bumps all over except on the scalp. He has seen our doctor and she has no clue. Gave him an anti-viral medication and benadryl. He is developing more bumps and the older bumps have turned hard and new bumps itch.