Suggest Treatment For Itching All Over The Body

Hello asking question for wife. She us 43 years old and about a month ago started to itch started out with just on her back and now is all over. We have been to two doctors 1st one gave her a steroid shot did not work. The second did blood work and that came up ok. Now they want us to spend about 800 dollars to do allergy tests. Just wondering if their is a simple solution before doing testing?