The National Heart, Lung and Blood Institute lists inflammation and narrowing of the airways in the lungs as asthma's primary effects on the respiratory system. The airways in people with asthma are swollen and easily affected by inhaled contaminants. Exposure to contaminants causes the airways to further constrict and swell, and cells in the airways produce excess mucus which exacerbates airway narrowing. These events trigger the symptoms of asthma.
According to the National Heart, Lung and Blood Institute, asthma is characterized by coughing, wheezing, shortness of breath and tightness in the chest. Mild to moderate asthma symptoms are controllable with inhaled medications that relax the lung's airways. When symptoms intensify, they are referred to as an asthma attack. During the most severe types of attacks, if the patient is unable to control the symptoms with his prescribed medication, medical intervention is required to stabilize breathing. Asthma symptoms can be fatal when left unchecked.
The exact factors that cause a person to develop asthma are unknown, but the National Heart, Lung and Blood Institute reports that genetic and environmental factors are suspected causes. In many cases, asthma runs in families and early childhood exposure to allergens, contaminants and infectious agents often triggers the condition.