Hi,
I can't say for sure what's causing your daughter's sudden symptoms. I developed allergies when I was in my mid-twenties. Prior to that, I had no problems with allergies, none when I was growing up. My mom had allergies all while she was growing up, but they went away when she was in her thirties. Allergies are weird like that.
I know my post wasn't particularly enlightening, but my point is that allergies can develop at any time.