For ground roles, you need to have been symptom free and therefore without treatment for four years or more. For roles in the air however it is imperative that you have no history of asthma. However, I recently read about the odd case (non too common either) where those with a childhood history of asthma have got in as aircrew. On the other hand, many cases are given no consideration whatsoever and are rejected as quick as possible.
There is no way to tell whether you will be considered or not for air roles if you have ever had just about any respiratory disorder. Some will get in, but it seems most will not.
are you certain? im fairly sure that if it was before 4 and non persisting one would be considered for aircrew, unless the system has changed.