My allergies:dust, pollen, trees, mold, grass, I get sinus congestion & Inflammation several times a day. Will immunotherapy prevent the Inflammation?

Likely. Immunotherapy is effective about 80% of the time in reducing the allergic responses which cause the inflammation. Of course, it must be accompanied by avoidance measures as well. Even more important, after 3-5 years of shots, many people continue to enjoy the improvement in symptoms even years after the treatment has been stopped. Talk to your allergist.