I've zapped away an oncoming cold twice this year, catching it as it was first coming on. I would recommend you look into North American Herb and Spice Company, particulary the Wild Oregano Oil and capsules for respiratory conditions for your son.
I would secondly highly recommend you check into an Elanra ionizer and perhaps an air ozonator from www.toolsforwellness.com
Lastly, and most importantly, I would have your son start with the Transfer Factor, and eventually move up to Transfer Factor Plus, and get his immune system up to 248% greater than what it is now. Of course all of the Dr. Clark and Dr. Richard Shulze cleanses and clean ups are paramount, and if you have access to a FIR (Far-Infrared-Sauna) sauna, you may wish to check out Dr. Sherry Roger's protocals via "Detoxify Or Die" at www.prestigepublishing.com There are a handful of doctor's and practioner's out there who have the Fscan2, and if you can find them, they could scan for the specific organisms that may be in your son. Of course the Beck Protocal's are yet another option.
My father has experienced great success in overcoming his respiratory issues and vertigo with using the Transfer Factor and Wild Oregano Oil capsules from North American Herb and Spice. Keep zapping! http://www.livingnow.net/vanderpool/ Remember that mold plate tests can be obtained through Dr. Sherry Rogers'. You can read more about respiratory conditions and Wild Oregano Oil through North American Herb and Spice or GOOGLE Dr. Cass Ingram and "respiratory conditions" or Wild Oregano Oil. This along with the Transfer Factor should greatly help. Please let us know if you pursue these, and gain any measure of success, in the future.