I also have what is now fairly mild Asthma, mostly exercise induced. I get airway constriction much more when sick, during allergy season, and it seems to come easier when cold as well. This morning on my last climb I got constriction in my airway again right before the top, I knew I should have eased back a bit but decided to push it anyway.
I don't use an inhaler anymore, mostly because I can feel when I need to dial back the exhertion level. When running I don't have a feel for it as well, though. Last time I went running I was pushing harder than normal and at about 3/4 mile left my airway started to tighten and I slowed and had to walk for about 10 minutes while trying to stay calm. I hadn't gotten it that bad in years. I also hadn't thought about carrying an inhaler for years until that point.
Asthma can be dangerous, I don't let myself get into situations where I know I could get an Asthma attack because it kind of freaks me out. We get temperature inversions here in the winter, where all the pollutants are trapped in the valley by the mountains. When that gets bad I just don't ride.