What Is The Treatment For Red Blotchy Rashes On The Chest And Arms?

I have a pretty constant red blotchy rash on my chest back and upper half of my arms. It is absent around my underarms though. I saw a doctor after I had it for about 4 weeks and they said they thought it was something (said the name, I've never heard of it), and it would go away on it's own in the next few weeks. Well it's been several months and it's still here. Help?