Answer:
have you taken any new medication lately? especially a "generic" form? they contain fillers from china and India that can cause serious allergic reactions. i got the same thing on my back after taking generic wellbutrin (bupropion) to quit smoking. it was horrible. the itching darn near caused me to lose my mind and i'd scratch until i was bleeding. try some benadryl. that was the only thing that helped me - and it took several days of benadryl to get it under control.