sounds like you have either contact dermatitis or severe case of athlete's feet.
soak the foot in epson salt and warm water to help dry out the blisters. preparation H also will help dry them out and calm down the itching because it contains witch hazel and cortisone. an antifungal cream (lamisil) and a cortisone cream application to the area for 1-2 weeks help too.
Have you ever tried Preperation H on your blisters? It sounds weird but I had tonnes of blisters when I started hiking and a ballet dancer friend of mine said that all the girls had Prep H in their bags for their feet. It worked like a charm for my blisters.