What Is It? Asthma is a chronic (long-term) lung condition. Air
passages narrow and become inflamed. This leads to breathing
difficulties and wheezing. Asthma ranges from mild to severe.
Some people have only occasional, mild symptoms. Others have
nearly constant symptoms with severe, life-threatening flare-
ups. During an asthma attack, the airways become inflamed. They
narrow as the muscles surrounding them constrict. Mucus produced
by the inflammation fills the narrowed passageways. As a result,
the flow of air is partially or completely blocked. Asthma
affects the lung's larger and smaller airways. What causes
asthma-related inflammation is not clear. But several
environmental "triggers" have been identified. Many asthma
triggers are allergens. Allergens cause the immune system to
overreact in some people. Common allergens include: Animal
dander and saliva Also high on the list of asthma triggers are:
Viral infections, such as colds and influenza Breathing cold,
dry air Environmental pollutants, such as: F