It might be that the itching causes the scratching, but that the scratching causes the skin sores. Sounds too simple, right? I saw a medical show in which a guy did this to his hands. He scratched so constantly that he caused thick, scaly, eczema-like skin sores, and he kept seeing doctors and they guessed all kinds of stuff. It took him several doctors to diagnose it properly. I think he was cured by a dermatologist applying a special tape that had steroids in it, on the places he was used to scratching (which both soothed the skin and also prevented his scratching), and finally when the raised sores went away, he could see it was his own fingernails and his constant irritation of the spots that actually caused the worst of the issue. Have you ever tried a steroid cream on the itchy skin?