Asthmatic children with the most severe allergies tend to have the most severe asthma. We used to think that asthma doesn't scar the lungs, but we know now that there is a process called airway remodeling that leads to problems in adulthood. There is a close association between asthma during childhood and chronic obstructive lung disease during adulthood that occurs mostly in people who have asthma during childhood and later smoke cigarettes. The largest increase has been in teenagers with asthma. We don't know the reason for the increase in asthma fatalities but we have reason to think that environment has something to do with it because fatal asthma is also concentrated in major urban areas among minority groups.
Nighttime cough is by far the most common asthma symptom in children.
There is no question that air pollution, especially ozone and oxides of nitrogen, act as triggers for asthma at any age. Inside air pollution is much more important as a trigger for asthma that outside air pollution. The most common and misunderstood indoor trigger is cigarette smoking which acts as a strong trigger even after the smoker is finished. The fumes of cigarettes are taken up by curtains and furniture and continue to act as an asthma trigger. Researchers have been trying to find evidence that food allergies act as a trigger for asthma for many years.