Joy, is your son on preventive spray? The steriod spray I mean.
Our son tried a month of Chinese medicine earlier on in July when he was first diagnosed of asthma. It did stop his flareup for a month. But then it got worse all in a sudden and he was having severe attack. I don't know whether it's Chinese medicine. But anyway we stopped giving him Chinese medicine and he has been all fine for over 3 months!