I was 23 when I left for my first Iraq deployment. I was healthy as a horse.
Now, I'm 29, have been there on four different trips totaling over 3 years of my adult life. 3/4 of that time I have been in Baghdad and similar industrial areas.
I currently have allergic reactions to many things that I was NEVER allergic to (I previously had no allergies) and I also have horrible asthma. It's forced me to reconsider my career options
So, I believe there is certainly something over there that is causing these problems...I'm not the only person with these types of issues. Sucks man.
Perhaps you could try this?
http://theblessedseed.com/It helps my wife's MS and Dystonia and it cured my friend's daughter's asthma, so you never know.
It's worth a shot if all else has failed.