My friend(70) woke up with 2 large red,swollen patches on her right arm.They were hot and squishy under the?

skin,no visible bite marks.she went to a clinic and was given 4 prednisone tabs.these are still hot at night even with ice packs thru the day.no fever or any other symtoms.Dr said allergic dermatitis....a vague answer,I think...no bedbugs either, oh,it DOES ITCH!!! Any ideas? No allergies known except for sulphs no weird foods eaten either...please answer