How to take care a baby to avoid having Bronchitis / Allergic Bronchitis???

My boy now is one year old. He just recover from this bronchitis / allergic bronchitis. Its takes around one month to fully recover. I am so sad to see him taking so many medicine. Doctor said that if not taking good care, it might be asthma in the future. I am so worried. Pls tell me how to take good care to avoid he being infection again. Pls help..........