Does he have reflux or GERD still???
I would look into this more.
It causes coughing and wheezing...
Sinus problems/infections also causes coughing. My Hubby has sinus problems and it drips and it causes coughing that goes on and on. It's hard to stop it.
"Nasal saline irrigation/rinsing" is also very helpful in keeping the sinuses healthy and clear of bacteria. My husband swears by this. Your son may be too young, so maybe not. Here is a link about it:
http://allergies.about.com/od/noseandsinusallergies/a/nas...
Here are some links about coughing:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid...
http://lungdiseases.about.com/od/termsdefinitions/a/chron...
http://familydoctor.org/online/famdocen/home/tools/sympto...
Perhaps switch to natural/organic or "safe" household cleaning products as well. I've heard this has helped a lot of people who suffered from illness or allergies. The fumes from chemicals can build up in a house, causing toxicity.
Take care, I really hope a solution can be found for your son.
All the best,
~Susan
www.cafepress.com/littlegoogoo