When do “seasonal allergies”end for the year?

2 Happily Married Americans asked:I live inMichigan,andhavebeentaking Zyrtec andNasonex tofight outside seasonal allergies sincemid-summer. Theleaves arejustaboutoffthetrees,butthegrass isstill green andwestill havesomeflowers. DoI havetowait until snowfalls togooffof[...]