Asthma is a reversible narrowing of the airways, and two problems hit at once. The muscle around the tube squeezes shut, which is bronchoconstriction. The lining gets swollen and full of mucus. A trigger sets it off, and a rescue inhaler opens it back up. Click through the attack.
Looking down a bronchiole
This is a cross-section. You are looking straight down the airway tube. Watch the opening, called the lumen, get smaller.
Pick a state to see the airway.
Pick a stateNormal · Attack · Rescue
👆 Walk through an attack
Triggers: exerciseallergenscold airsmoke
What's happening
1 · Bronchoconstriction
The ring of smooth muscle around the airway tightens. That squeezes the tube narrower.
2 · Inflammation
The lining swells and pumps out mucus. That clogs the little bit of opening left.
Signs: shortness of breath (dyspnea) and a tight chest, wheezing, and a cough that is classically worse at night. Because asthma is reversible, a bronchodilator, which is the rescue inhaler, relaxes the muscle and opens the airway again.