Prone To Cold And Cough. Diagnosed Hyper Reactive Airway Disorder. Best Way Of Treatment?

Question : My Son who is 12 year old has been quite prone to cold and cough since last couple of years. recently he has been having cough for last 3-4 weeks and that is when we consulted two doctors. As per them he has wheezing and have diagnozed as hyper reactive airway disorder. When I further read about it over the Internet I found that there are different names for the same problem. Some people classify it as Asthma and by and large the medicines or treatment subscribed are very similar. As per my prelim knowledge there can be three reasons for this problem i.e. chronic or genetic asthma, exercise induced or allergen induced. As of now my doctor has said that it is most likely allergen induced and kid should be fine after 15-16 years of age. I would appreciate if somebody can help me get the answer like how to be sure the reason for his problem and what could be the best way to move forward for treatment .

Our doctor has prescribed Salbutamol and Budecort 50 inhalers for the time being. I was worried whether once we start these inhalers whether he would need them on constant basis or he should be fine once he gets over with this cycle of cough. I suppose Budecort might have some side effects too so if would be glad to know of any better medicines or therapy to get over with this.