A person with asthma experiences inflammation of the bronchi, even when symptoms are not present. This causes a narrowing of the airways and an increased sensitivity to allergens or other stimuli. Exposure to these triggers often produces symptoms such as coughing, wheezing and an inability to breathe normally (shortness of breath).   

Asthma primarily affects the bronchi, the large passageways that allow air to travel between the trachea (windpipe) and the lungs. The inner lining of these bronchial tubes is called the bronchial mucosa, and it houses two important contributors to asthma:

• Mucous glands. These glands normally produce the proper amount of mucus to lubricate the airways. However, during an asthma attack they produce too much mucus, flooding and blocking the airways.
  
  
• Inflammatory cells. These cells (including mast cells, lymphocytes and eosinophils) trigger inflammation in response to something the body perceives as a threat, such as allergens or irritants. The inflammation, in turn, allows for more blood to flow to the area, carrying cells to fight the threat. This is a natural system designed to protect body tissue, such as the lining of the bronchial tubes (mucosa). However, during an asthma attack, the tissues remain inflamed for extended periods of time.

During an asthma attack, exposure to an allergen or other stimuli (such as exercise or cold air) causes mast cells in the tissue of an asthmatic’s air passages to react by producing histamine, leukotrienes and other chemicals. These chemicals cause the following chain reactions:

• The smooth muscle of the bronchi goes into bronchospasm and tightens, constricting the airways.
  
  
• The tissues lining the airways – which are often inflamed in asthmatics – become further inflamed, further narrowing the airways.
  
  
• The inflamed tissues produce excess mucus that fills and obstructs the airways.

The combination of smooth-muscle constriction, tissue inflammation and mucus secretion significantly narrows the diameter of the airway, a process known as bronchoconstriction. When this happens, air is trapped in the lungs, forcing the individual to expend great effort to move air in and out.

Because airways are narrowed during an asthma attack, a person may experience chest tightness, coughing, wheezing and shortness of breath. In severe cases, where breathing becomes very difficult and low blood oxygen levels occur, asthma attacks can be fatal. About 5,000 deaths each year are attributed to asthma, according to the American Academy of Allergy, Asthma and Immunology (AAAAI).

Low blood oxygen levels can also be dangerous during pregnancy. Since a fetus depends on oxygen in the mother’s blood, uncontrolled asthma during pregnancy can lead to low birth weight and other complications.

Someone suffering through an asthma attack may appear to be gasping for breath. But in fact, it is easier to breathe in during an asthma attack than it is to breathe out. As more air flows in, it becomes trapped in the lungs, which become overinflated. Asthmatics continue to try to push this ever-increasing amount of inhaled air out of their lungs and through a narrowed airway, usually with limited success. Medications and other strategies are required to reverse the airway-narrowing process, allowing air to flow in and out of the body more easily.

According to the National Heart, Lung and Blood Institute, approximately 20 million people have been diagnosed with asthma, and 9 million of these patients are children. Asthma affects people of all ages. However, it often develops in childhood. The condition is more common in boys during childhood, but after puberty, more women have the condition.

Although asthma affects people of all races, African Americans are more likely to be hospitalized and die from the disease, when compared to Caucasians.