Good question. At MEPS I told them that I had used a breathing treatment once when I was a little kid. That's all I remembered. Ofc, they DQ's me, and requested med records from my physician. I went to my pediatrician whom I hadn't seen in years and got the records, and as I was looking through I freaked out because I saw she had diagnosed me with "asthma exacerbation" back in 2008 or smth. I called her because I was certain it was an error, but she said that my symptoms were suggestive of asthma. So I had to get a pulmonary function test done to prove that I am currently asymptomatic.
Edit: It was actually back in 2006 when I had the inhaler treatment. The scary part was, when I thought about it later, I remembered that I actually had an inhaler to carry around school. I NEVER used it though, which is why I completely forgot about it. I even asked my own mom if I ever had asthma, and she said no. So if it wasn't for me checking my medical records and speaking with my pediatrician, I never would have known.