My doctor told me to try exercising more in spite of me having a low BMI, being unusually active, and having asthma, since the drugs which are available for people with asthma mainly treat the symptoms. If you want to avoid needing them in the first place, increasing your stamina is the only fix.

I was diagnosed with asthma just over a year ago. (The only symptom I've ever had is that in winter when I get a cold, I cough for the rest of the year unless I go on steroid inhalers). My lung capacity dropped by 22% when I did the methacholine challenge test (inhaling an irritating chemical) but I barely noticed it. This is probably related to the fact that I started swimming competitively when I was eight, and my lung capacity is already much higher than the average for someone my height and weight. (I don't know if I could have reached this point if my asthma had started before I began swimming, though. Ironically enough, I'm pretty sure my current asthma is caused by too mcch chlorine exposure over the years, and I'm considering taking a summer off from lifeguarding to "detox" myself enough that I can test negative on the asthma test.)