I had what I thought was allergies since high school. Sounds like what you are describing Dan, but mine would last much longer, usually the rest of the day. Benadryl would help but make me very drowsy. I had all the allergy tests done and they found a slight allergy to dust mites but thats most people. I finally went to see an ear, nose and throat doctor about a year ago. He said I had a slightly deviated septum, an inflamed somethingorother, and I don't remember what else. The point is, he gave me a prescription for Nasonex. The next day I had another one of my "attacks", but I haven't had a single one since. The Dr. said the medicine doesn't work immediately and thats why I had the single attack but that there is no reason I can't stay on the spray indefinitely. Two quick sprays in each nostril once a day (I do it right after the shower when my nose is clearest) and I can breathe better than I ever remember being able to breathe before. I am also able to sleep much better breathing through my nose which I never could do before.
If it bothers you bad enough, get it checked out. I don't know why I waited so long.