Flonase will definitely help with your allergies but has some extremely negative side affects. It is a corticosteroid and causes, among other things, sleep disruption. Totally not worth it. DO NOT USE FLONASE. DO NOT USE FLONASE.
I don't recall trying Flonase but I had extremely good results with my allergies when I was using another nasal corticosteroid, Nasonex. I used it as sparingly as possible, like once every 3-5 days just to keep the misery at bay through ragweed season, but after using it through September and October for 2-3 years I learned about long term side effects like glaucoma and cataracts and I won't touch it again.