First of all I want to welcome you to HealingWell. I am sorry to say I don't have any suggestions for you. I am 56 years old and have had asthma for five years. Hopefully, someone will come along soon who be able to give you some suggestions.
Does your soon see an allergist? If so, you might call their office and ask for ideas. I am sure he is not the only seven year old with this problem.
Please keep coming back.