Asthma is a chronic inflammation of the airways with reversible episodes of obstruction, caused by an increased reaction of the airways to various stimuli. Asthma breathing problems usually happen in "episodes" or attacks but the inflammation underlying asthma is continuous.
Asthma is one of the most common chronic disorder in childhood, currently affecting an estimated 7.1 million children under 18 years; of which 4.1 million suffered from an asthma attack or episode in 2009.
An asthma episode is a series of events that results in narrowed airways. These include: swelling of the lining, tightening of the muscle, and increased secretion of mucus in the airway. The narrowed airway is responsible for the difficulty in breathing with the familiar "wheeze".
Asthma is characterized by excessive sensitivity of the lungs to various stimuli. Triggers range from viral infections to allergies, to irritating gases and particles in the air. Each child reacts differently to the factors that may trigger asthma, including:
Source: American Lung Association Website 3-3-2011 “Asthma and Children Fact Sheet”