Abpa
This sounds like ABPA which is a fungal infection (Aspergillosis). The initial test is to check IGE level and the treatment is usually Prednisone. I suffered long term from ABPA. I was on Prednisone for a long time (2 and half years), but was then switched to Xolair (injections every 2 weeks) which cleared it up for me without the risks and damage of long term steroid use (diabetes, osteoporosis, weight gain, etc). The challenge is that Xolair isn't really approved for CF. You need a good allergist who help get it approved if that is the right treatment for you. If you do get an ABPA diagnosis, at least ask about Xolair before getting on the steroids. They may also try you on anti-fungal meds. They didn't work for me.