Suggest Treatment For Chronic Phlegm Discharge From Nose

hi sir, i want to know that i have a problem that i have allergies to some food items and dust as well as told to me by my ENT specialist doctor after allergy test.as a result of which i get bulgum coming out of my throat all day/night.even on avoiding such items i am still facing such problems as a thick wet bulgum from nose and throat is always there.i am facing this problem from last 5-6 years.i am 21 year old. thanks and waiting for your response!