Level 1 is the preliminary symptoms of asthma, there is a person at least once a week and rarely have symptoms at night or wheezing during the night a month, just not more than 2 times/month. When reviewing the performance of the lungs that is normal.
Level 2 is the least severe form have asthma by once a week, but not in the size frequency every day. During the night, to form arms twice/month.
Level 3 is a moderately severe wheezing symptoms are daily. The wheezing at night once a week later than average, and the symptoms that will affect daily life.
Level 4 is the most severe symptom is wheezing all the time and is very often during the night. Symptoms are interfering with daily life greatly.