Your airways suddenly narrow and swell. You may struggle for air, cough up mucus, or hear whistling when you breathe.
It’s not clear why this happens to some people, but lots of things could trigger an attack, including pollen, dust, smoke, exercise, freezing air, a cold, and stress.
Your doctor can help you figure out what causes yours. They might prescribe medication for you to inhale during an attack to help you breathe more easily.