Red itchy area showed up on lower back out of no where wed. thurs it grew larger & bumpy; fri. tons of tiny blisters formed. super itchy & sensitive?

Shingles: The best way to diagnosis a rash is to actually see the rash and/or feel it, so it is difficult to provide information based on this question. The rash of shingles usually starts as a red itchy (often painful) area, and then develops blisters. Shingles rash usually occurs on only one side of the body, and stops abruptly at the spine when it is on the back.