What Causes Red Rashes And Blisters On Lower Back?

My wife has 7 to 8 large clear blisters on the area of the small of her back, above the buttocks. We think they could have possibly been caused by a blister beetle, but we have no tangible evidence. She discovered them and showed them to me. Also, there was a rash close to these blisters. She says that she had inadvertently scratched one of the blisters and that they spread. I went on-line to find out more about blister bugs and saws photos that resembled the blisters which were, indeed caused by blister beetles. I could find nothing that gave a treatment. We applied a dermatitis type of ointment. The next day the blisters appeared to be better; however, tonight the blisters appeared again much the way they originally appeared.