Cause And Cure For Itchy Rashes On Back

For the last few weeks, a few times a day, I get a sudden onset of extreme prickly "rash" all over my back, although there are no external symptoms -- it's like someone suddenly rubbed Ben Gay mixed with cactus needles all over my back -- it starts with small pricky feeling and then, within about 30 seconds, all of my back is "aflame." Then it will subside somewhat after about 10 minutes but not really go away. It's somewhat itchy, but mostly it hurts like prickers all over. And then, once, I felt the feeling a little bit after I had to sneeze about 4 times in a row. Very strange! Has anyone ever heard of this?