I know when I was applying some 25 years ago I put it down on my form and it meant I had to supply all the zillions of medical records they then requested, but ended up not having a problem. But I think there's a huge range, and that's what they're looking at. Whether you took Claritin a couple times OTC each season, or had to get regular allergy shots. Obviously going to be one of those huge "it depends" situations!
I will add, and this may be entirely coincidental, that three years in a row at West Point in early May (prime allergy season) I ended up in the hospital with bronchitis!