I had asthma as a kid and still carry an inhaler, just in case. I reported it the first time I got a first class medical, jumped through some hoops, but got the first class with no waivers. I had to get a letter from my regular doctor just stating my asthma is not a factor and under control. I have been flying for a regional for the past 5+ years, with no problems, and every 6 months for my medical I just state no change as far as the asthma box. I have just passed a indepth medical with a Japanese carrier with no problems, there was a lung capacity test and I passed that fine. Just keep it on the downlow, and don't bring it up, but it should never be a problem causing you not to get hired. You can send me a message if you have any more questions, good luck.