Allergic cough : I would suggest the following. CT scan of the Sinuses and Chest to rule out any underlying problem as a primary cause or as aftereffect / sequel of the allergy as you have a problem of more than a year. In consultation with your Doctor / ENT Surgeon. Tapering dose of oral steroids like deflazacort over 3 weeks. Cetirizine with montelukast. Vitamin A & Vitamin D in therapeutic dosage. Continue with multivitamins- supports the immunity system. Steroid nasal spray as was prescribe already. Antibiotics only if there are signs and symptoms of infection. Steam inhalation. And Most important to keep away from the allergens causing gall such problems. Your keen observation alone can find what to avoid. This is basically the mainstay of your treatment. Get a Doctor with whom you can discuss this and get a proper examination and prescription.