I had an asthma when i Joined the marines and the recruiter just told me to lie
I was nervous as heck when i was in the gas chamber because the instructor kept saying that if you have any health problems.. (icluding asthma) you need to let us know.. And i didnt, still passed and did my 4 yrs.
.. its all in your head i guess, I sure didnt want to get left behind or get booted after all the hard work that i did.