I Have Been Getting First On My Leg,starting With A

I have been getting first on my leg,starting with a dot, like a bug bite then little dots that form a perfect circle and become very red. They don't hurt or itch but then I get satellites of the like surrounding the original circle.
I now have them on one of my hands and both of my arms. They never go away, the original one of my leg has been over a year. No one seems to be able to tell me what is causing this. Any ideas??