he should be on 2 types of inhalers- one asthalin
for relief of acute cough symptoms & a steroid
inhaler like budecort
for controlling frequency of attacks. please check if tehnique is correct & ur son is geting adequate treatment.
other main issue is that, avoid all that is causing allergy
in him like dust, smoke, agarbati, saambrni smoke and clean his mattress once in 3 days & sun dry it. these things can reduce the episodes.