Black itchy spots on legs. Steroids?

I get these tiny blisters coming up from my feet to inner thighs which starts with itching and as it increases and I scratch it turns to become dark black spot. Visited a dermatologist few months back and she had put me on antibiotics which helped to reduce until I was on the course, however it has not reduced but only increased since then. I had a similar problem around 5 years ago which was much severe and then I had to take small dose of steroids for a month long as prescribed by a dermatologist. This did not help either, the allergy or whatever it is called disappeared on its own after almost an year. This coming back has really made me worry as I do not want to take any form of steroids again. Is there a solution for this without steroids? Please help!