allergies

Dear Sirs,
Recently Ive been having an unusual amount of phlegm/and difficulty breathing for about 4 months,
im allergic to dust and i live in a very dusty envireonment,so now im looking for an antihistamine that will help reduce the congestion in my sinuses especially my throaght and if possible help me with my breathing since the allergies seem to affect my breathing and it feels like its being obstructed.
So basically i need input on what kind of medication i should be looking for since theres no hope of me moving out of this country any time soon.

Thank you,
Koji Gabriele Inoue