Asthma is a disease in which inflammation of the airways causes airflow into and out of the lungs to be restricted.

When as asthma attack occurs, mucus production is increased, muscles of the brochial tree become tight and the lining of the air passages swell, reducing airflow and producing the characteristic wheezing.

In an acute episode, bronchiospasm is followed by mucosal infalmmation, increased brochiol secretions and the formation of mucus plugs.