What Is The Treatment For Allergic Rhinitis?

I have an 8 year old nephew, who has allergic rhinitis. He suffers from cold and runny nose, headache most of the days of the year.He can t sleep well at night. We have tried loads of different medicines. Finally we see a little relief after using duonase nasal spray(containing azelastine and fluticasone) .I wanted to know, 1. does this medicine have any side effect on long term use, such as growth impairment, or hoarseness of voice? 2. Will this drug have an effect on the in- vivo production of steroid hormones in the body? 3. Will this drug be addictive or have rebound effects once it is stopped? 4. Do we need to taper this drug while stopping as with other steroid prescriptions?Kindly help me with answers..