Asthma Health Article

Definition

Asthma is a chronic (long-lasting) inflammatory disease of the airways. In people susceptible to asthma, this inflammation causes the airways to narrow periodically. This narrowing, in turn, produces wheezing and breathlessness that sometimes causes the patient to gasp for air. Obstruction to air flow either stops spontaneously or responds to a wide range of treatments, but continuing inflammation makes the airways hyper-responsive to stimuli such as cold air, exercise, dust mites, pollutants in the air, and even stress and anxiety.

Description

The changes that take place in the lungs of people with asthma make the airways (the "breathing tubes," or bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that do not affect healthy lungs. In an asthma attack, the muscle tissues in the walls of the bronchi go into spasm, and the cells lining the airways swell and secrete mucus into the air spaces. These two actions cause the bronchi to become narrowed (bronchoconstriction). As a result, a person with asthma has to make a much greater effort to breathe.

Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscles to contract and stimulate mucus formation. These substances, including histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area, which play a key role in the inflammatory response. Many patients with asthma are prone to react to such "foreign" substances as pollen, house dust mites, or animal dander. These are called allergens. An acute asthma attack can begin immediately after exposure to a trigger or several days or weeks later.

When asthma begins in childhood, it often affects a child who is likely, for genetic reasons, to become sensitized to common "allergens" in the environment (atopic person). When these children are exposed to house dust mites, animal proteins, fungi, or other potential allergens, they produce a type of antibody that is intended to engulf and destroy the foreign materials. This makes the airway cells sensitive to particular materials. Further exposure can rapidly lead to an asthmatic response.