About Asthma

Common symptoms of asthma are wheezing, coughing, tightness in the chest and difficulty breathing.

Asthma affects 17.3 million people in the United States, including nearly 5 million children. Although the disease can strike at any age, 50 percent of all cases are first seen in children under age 10.

Among children, boys are twice as likely to be affected than girls are. Childhood asthma may fade with age. Environmental factors trigger attacks in 85 percent of those with the asthma, but the disease does appear to have a genetic component as well.

Four to 5 percent of the United States population has asthma; however, among those who have a parent or sibling with the disease, the incidence jumps to about 20 to 25 percent.

For most people with asthma the wheezing, shortness of breath, coughing and tightness in the chest that come with an attack are essentially the manifestations of an allergic reaction. When an allergen (an allergy causing substance) enters the airways through the nose or mouth, it interacts with a specific antibody causing the release of chemicals — histamine, leukotrienes and prostaglandins.

These chemicals trigger the contraction of the smooth muscle that lines the airways. The airway linings become inflamed and a thick, clogging mucus is secreted. This muscle squeezing, swelling and excess mucus blocks airflow in and out of the lungs, making it difficult to breathe. Four to six hours after the initial exposure to the allergen (the late-phase reaction) an army of white blood cells arrives on the scene causing a second bout of inflammation that again leads to difficulty breathing.

While it is not yet known what triggers an attack in nonallergic asthma, the body’s reaction is the same. The chemicals released cause the same affects and the patient suffers the same wheezing and/or coughing symptoms.

While asthma episodes can be triggered by allergic and non-allergic mechanisms, the most common triggers are allergies to pollen, animal dander (particles of hair and skin) and insect droppings present in dust.

Other triggers include: exposure to environmental pollutants and chemicals, cold, dry air, emotional stress, upper respiratory infection, sinusitis and postnasal drip, exertion, and abrupt changes in the weather, as well as drugs such as Aspirin, non-steroidal anti-inflammatory medications, sulfites added to foods and certain medications, and beta-blockers.

Exercise is also known to induce contraction of muscles that line the airways in a phenomenon called exercise-induced asthma.

The frequency of asthma attacks is highly variable. Some patients may have very infrequent, brief attacks, while others may suffer nearly continuous symptoms. According to the National Institutes of Health, asthma has four levels of severity: mild intermittent, mild persistent, moderate persistent and severe persistent.

In the mildest forms symptoms appear briefly, less than twice a week while the most severe form is characterized by continual symptoms, prolonged crises, limitations to physical activity and lung function which is below 60 percent of normal.

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