I Have A Belt/perimeter (1/4 - 3/4" Wide) Of Little

I have a belt/perimeter (1/4 - 3/4" wide) of little birdshot sized bumps (blisters w/clear liquid contents) surrounding the area of 2 large (2-3% ea.) abrasions, 25 days old, from bike wreck... my clinician's got me doing wound care w/silvadene twice daily and on lots of bactrim & clindamycin, but this belt of bumpy and extremely itchy area makes me wonder what the cause & cure is... thanks