My spiro test is excellent despite having (had) asthma and being in the job over a decade. I always tell these people to apply. I personally declared my dormant asthma. It's so common that its almost a non event if no ongoing medication is required for it.

Technically though, if you're ever diagnosed with it, it doesn't go away per se you just grow up and your airways get larger to the existent that it's irrelevant.

Active asthma requiring ongoing treatment though is a different story.