Introduction

What Causes Childhood Asthma?

The cause of asthma is multifactorial and includes both hereditary and environmental factors. Most cases of asthma are thought to be related to the presence of allergies, however not all persons with allergies have asthma and not all cases of asthma can be attributed to allergies.

Asthma Triggers

• Cold, dry air
• Exercise
• Tobacco smoke
• Fumes (paint, exhaust, etc.)
• Viral respiratory infections (syncytial virus, parainfluenza, rhinovirus, adenovirus, and influenza viruses)
• Environmental allergens such as house-dust mites, molds, and cockroach antigen

Genetic Factors

Because asthma tends to "run in families", researchers believe that some children may be genetically predisposed to developing asthma. It is likely that environmental allergens serve as a trigger for asthma in children who are genetically predisposed to developing the condition.

Asthma and GERD

Studies have shown that a large proportion (about 75%) of people with asthma, including children, also have gastroesophageal reflux disease (GERD), the cause of heartburn. The physiologic connection between these two conditions remains unclear. Theories being investigated include the possibility of "microaspiration" (inhalation) of very small amounts of gastric contents into the esophagus causing reflexive reaction of the airways. These patients typically have symptoms of asthma following an episode of heartburn or that are worse after eating or exercise, and do not obtain relief from asthma therapy alone.

Exercise-Induced Asthma

Many people have asthma that is triggered only by exercise, a condition known as exercise-induced asthama (EIA). Symptoms such as cough, chest tightness or pain, or wheezing usually develop after a brief period of vigorous exercise and resolve spontaneously within 30-60 minutes. Exercise-induced asthma is followed by a refractory period of 30-90 minutes, during which further exercise is followed by a shorter, less severe asthmatic response.

In addition to the use of pharmacologic treatments administered shortly before the exercise, EIA can be managed by inducing a refractory period and selecting a climate condition (warm moist air, minimal pollen) and sport type (swimming, etc.) that are less likely to provoke EIA. A "warm-up period" before a sport event is an effective way of inducing the refractory period.