What Causes Itchiness And Swelling Of Ankle Caused After Changing Footwear?

A few days ago I bought a new pair of shoes (ankle boots) I wore them for 2 days at work to walk them in. Then noticed my feet were getting sore. So I switched back to an old pair that was flat and comfortable. I wore them for two days and at the end of the two days my right ankle swelled up not tooo much but was definitely noticable to the naked eye and was very sore to the touch but also very itchy at the same time. Its was sore scratching it but felt good when I scratched it. Any idea of why it would scratch?