What Causes Blisters And Itching On Hip?

Approximately 1 1/2 yrs ago I had a welt on my hip. The next few days it blistered. I thought it was a spider bite and just dealt with it. Last wednesday I ran a low grade fever and the welt came back in the same place and has blistered again. It was very itchy and burned and had sharp shooting like pains in my hip. Haven't gone to the doctor but I'm curious to know what could be the cause of this happening again.