mnmthomson,
You are lucky that the Pseudomonas isn't rearing it's head. I encourage you to do the whole allergy protection thing. You will be shocked at the diffence at his health. My doctor tells me even the simple act of ripping up the carpets has brought immediate relief to her patients. And with each thing you do, you will see the infections subside as your son's inflammation cools down. There was a point that I was on Tobi without a break. It made no difference at all and I eventually developed total resistance to it.
When I stopped the Tobi and changed my lifestyle accompanied by the right meds, I stopped having the constant infections. And you should know, I was one of those people that needed IV meds, coughed up blood all the time -- so I was pretty severe. So if I can get off Tobi and not have continual infections -- maybe your son can too.
I have written about how to reduce inflammation in so many posts. You can search for them and under advanced search, you can go back further than the recent posts. There is a lot of info on what you can do -- act now and prevent permanent lung damage.
When the airways are inflammed, exacerbations result. They may seem like infections, but can be caused purely by inflammation, This is when an antibiotic will have no effect and the reason that some people are on an endless cycle of antibiotics without much success.
There is an asthma component to CF that many doctors don't recognize although they prescribe asthma medicines. I waws wondering if it was your doctor or someone else made these suggetiond to you. Because it is imperative that you see a doctor who recognizes the asthma component so that your son is taking all the medicines that can help reduce and control inflammation.