Over The Past 4-5 Months Now I Seem To Have

Over the past 4-5 months now I seem to have developed an itchy and bumpy rash in the left collar bone region. It comes and goes as it pleases, but the rash is a regular occurrence and no matter how much I itch, it still persists on being itchy. I don't know what could be causing this. I have no known allergies or reactions to cleaning/washing products.