Suggest Treatment Or Blisters On Hands

While in FL my husband helped sister with yard work....(3 wk ago) First had what we thought was poison ivy on arms...cleared up with OTC med....then broke out with blisters on hands that are defying tx.....currently on PO prednisone burst pack and Betamethasone cream for hands....old blisters clearing up, but new ones forming ...they itch, get big (cm ) and even get blood in them.....Have been told there is a shrub of some type in FL that is bad and difficult to clear.....we never was any poison ivy vines