When children don't feel good they misbehave more. My youngest son also had asthma and food allergies at a early age. Once we got those under control the behavior issues got better also. You may want to see if he has some food allergies that is adding to the problem. A pediatric allergist told me to keep a journal on him of everything he eats. If he starts showing signs of asthma or acting up, check the journal for foods in common during the last time he acted up. Sometimes he would show a problem with a food by saying he didn't like it or it made him have a tummy ache. Some would cause dry spots on his skin, especially around the inside of the elbow and on his back. He also had the skin tests and we took him off about everything, dairy, beans, peas, nuts, corn, peanuts, wheat. The list went on and this was when he was a year old. Bleached white bread was fine so we had to check if they used the bleached white flour in pancakes and everything else for a while. He did out grow most and the only things he had trouble with when he got older was bananas, nuts, peanuts and chocolate.
If your son is allergic to peanuts watch the Albuteral inhaler. My son kept complaining that his asthma felt worse after using it and when the doctor checked into it she found that there was peanut oil used in the off brand. That was years ago so they may have changed that now though.