This is a topic I know, oh, too well about. . . I've found that the best way is prevention. I try to keep the generic of Claritin D, Loratadine (works just as good as name brand) in my system at ALL times! . . . But when there's slip ups in my routine allergy pill taking or the wind has just stirred up so much guck in the air that the routine is ineffective, I use a combo of items:
Allergine eye drops (very handy), Zircom nasal spray, I continue taking the OTC medicine, but I'll add sinus relief medicine at night when it feels close to an infection.
The thing that helps the most is a Neti Pot, if you have one. Simply put 1/8th teaspoon of iodized salt in 8 oz. of luke warm water in the Neti Pot and use it to drain each nostril. The process is uncomfortable and the feeling in you nose during the draining is unpleasant, but your nose feels so good afterwards. Doing this every night for about 5 to 7 days really does the trick for me.
I also tend to get massive sore throats from sinus troubles. I use "Traditional_Medicines: Throat_Coat_Tea" Traditional Medicines also has teas for sinuses and allergies. They're tasty and soothing.
Lastly, when all else fails, I seek the help of my nose and throat doctor. I keep his business card handy. I noticed you have an allergist. Has he/she not given you more options?
There's also a procedure I'd heard of (an in and out minor surgery) where your nostril nerve endings that are sensative to allergies can be clipped back. I've had some people I know go through the surgery and rarely had colds afterwards and allergies are gone, but then I know of others who've had bad experience with the surgery. I guess it depends on the doctor. I haven't done the surgery yet myself, but it's an avenue you might want to consider. Just make sure you do your research.
Good luck! Feel Better!