The airways can get inflamed, contracting the smooth muscle and narrowing the airway. Many villains can inflame someone's airways. One of the big villains is smoke, particularly when children are exposed to smoke in the home. Other triggers can come from dust, pollution, pets, exercise, or getting a cold. Just as the triggers of an asthma attack can vary, so can its effects.
Attacks range in severity from person to person, from wheezing to a seeming inability to breathe.
In rare cases, asthma can be fatal. Doctors used to think that it all began when people had allergies, and developed asthma as a result. It's now thought that people have a genetic predisposition to asthma, as well as allergies. But environmental factors are also important. For example, if a parent smokes around a baby, the baby is more likely than other children to develop asthma.