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What is asthma?

Asthma is a chronic inflammatory condition affecting the lungs. It is characterized by reversible or at least partially reversible constrictions of the bronchi in the lungs. Bronchi are muscular tubes that carry air throughout the lungs, transporting it to and from smaller airway branches called bronchioles.

Thumbnail diagram of respiratory system

With asthma, the walls of the bronchi are inflamed and swollen. This narrows the airway and makes it more difficult to breathe, resulting in wheezing, breathlessness, or coughing. Acute asthma attacks or episodes increase this effect by constricting bronchi muscles and producing excess amounts of mucus. The diameter of the bronchi may decrease to the point that very little air can travel in or out. This causes the affected person to cough and wheeze, feel tightness in their chest, and struggle to breathe. Although the cause is not clear, asthma attacks can occur at any time but are especially frequent at night and in the morning. Severe asthma attacks can be life-threatening, often requiring immediate medical attention.

About 25 million people in the United States have asthma. An estimated 7 million of those affected are children, making asthma one of the most common chronic diseases in children. Before puberty, asthma affects more boys than girls. After puberty, it affects more girls. The condition is more prevalent in urban areas than rural and in those of African and Hispanic descent than in Caucasians. Asthma is not currently preventable or curable, but it is controllable and most people who have it can lead active, relatively normal lives.

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