I Have Developed A Rash Behind My Ear. The Rash

I have developed a rash behind my ear. The rash is a bunch of small clusters of bumps and extremely itchy. I applied a cream for the itchiness and when the cream wears off it begins to throb and the area becomes a deep purple and is swollen. This has happened on my fingers and toes. It takes about two weeks to go away. Any ideas what it could be?