My kids came at 25 weeks and were constantly sick when they started being exposed to people and struggled with illness-induced asthma for their first several years. I did a few things that may or may not have helped eliminate it:
1) Always lived at least a mile from the freeway.
2) Did not use weed killers in the yard.
3) Did not use air fresheners in the house.
4) Did not let them be exposed to even 3rd hand smoke.
5) Gave fish oil, vitamin D and probiotics
6) Gave lots of fruits and veggies (sigh, I wish they still ate so well)
It may be pure luck but they do not have asthma at all now. I have albuterol ampules for emergencies but they are off the steroid inhaler and the singulair (which I have no idea if it helped because the sickness was constant and maybe singulair kept it from being even worse, but maybe it did not).
I wish I could know if their current health is luck of the draw or if the above really helped. But they haven't even seen the pulmonologist in 2 yrs. This from a boy who needed oxygen his first 4 months!
Hopefully things improve soon. Watching your child struggle to breathe sucks.