What Causes Itching On Shin, Knees And Scalp While Having COPD?

I ve read on here that their is no known cause for this, and I have been trying to figure out what I have.. My shins itch so bad and sometimes my knees also. My scalp started itching at about the same time I had my first break out.. I have the rash to pop up other areas too.. I have copd, could this have triggered this rash...