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How do asthma attacks narrow the airways of children?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — respiratory disease The bronchioles of the lungs are the site where oxygen is exchanged for carbon dioxide during the process of respiration. Inflammation, infection, or obstruction of the bronchioles is often associated with acute or chronic respiratory disease, including bronchiectasis, pneumonia, and lung abscesses.

During an asthma attack, the airways of children—and adults—narrow through three primary physiological processes triggered by the release of chemicals from the immune system in response to an inciting factor:1

Smooth muscle contraction: The smooth muscle surrounding the bronchi undergoes spasmodic contraction, which physically constricts the airway.21
Inflammation: The bronchial tubes experience swelling and inflammation, further reducing the space available for airflow.1
Mucus secretion: There is an increased production of abnormally viscous mucus by bronchial glands. This mucus can clog the air passages, often acting like a one-way valve that allows air to be inspired but prevents it from being expired.21

Together, these factors create significant airflow obstruction, making breathing difficult. In severe cases, this obstruction can become life-threatening if the bronchi become completely plugged with mucus.21