Hi, welcome to the forum, important possibilities are contact or allergic dermatitis, Scabies, Vasculitis. A systematic evaluation is needed by a Dermatologist. Yes, blanket can be a reason for contact dermatitis, but before that other possibilities should be ruled out.
There is possibility of Chigger bites which can also cause vesicular lesions which are painless initially but later they can manifest as cutaneous reactions include raised lesions, rash, hives and bullous lesions, and are associated with itching. Most often, the legs and trunk line are affected.
You need to give history of any outdoor activity and tape stripping followed by visualization with microscopy will help to establish the diagnosis. In such case, vigorous cleansing with soap and water should be done. Clothing should be washed in hot water or treated with pyrethroid insecticides to kill mites.
Treatment includes, continue with anti histaminic and glucocorticoids against prescription. I suggest you to consult a skin specialist. Take care and regards.
benadryl! Is it just the blanket? Have you washed it? It could be the dye in it, or if you have changed your laundry det it could be from that. Try washing it and see if you still have a problem.