I took the flu shot on 10/06/2020 and started having painful,itchy rash to left underarm on 10/8, by 10/9 it felt as though someone was stabbing me with a hot knife and constant intense burning and numbness below the area. 10/10 I started getting a red, itchy rash to left shoulder blade area. I was prescribed prednisone and Valtrex. I had some triamcinolone I used for the itchiness to back and voltaren gel (lifesaver) on underarm rash. I've been using the meds for 2 days and while the blisters are still present they aren't as painful but back is still itching immensely.