This would explain the ebb and flow of your symptoms. In fact, one of the reason allergies are so hard to treat is because no two people suffer exactly the same. Nobody knows for sure. The immune system is filled with mysteries we're still trying to uncover. And the tendency to get allergies is definitely inherited.
Allergies usually begin in childhood.
But they can develop at any age for the first time. It's not unusual for new symptoms to develop in people in their sixties. It's a measurement of the amount of pollen in the air, usually reported as grains of pollen per cubic meter of air. Not all measurements produce the same results. Counts taken a distance away from where you live may not be accurate for your area.