How To Treat Severe Itchy Rashes On Ankle Inspite Of Using Hydrocortisone Cream?

I have an extremely itchy blister type rash on the back of my ankle . It has spread in a couple of days and I have been using Hydrocortizone cream for itching but it is also very dry. I also have the red blister like spots on other ares of my feet. What do you think it could be ?