When you breathe normally, muscles around your airways are relaxed, letting air move easily and quietly. During an asthma attack, three things can happen: Bronchospasm: The muscles around the airways constrict (tighten). When they tighten, it makes your airways narrow. Air cannot flow freely through constricted airways. Inflammation: The lining of your airways becomes swollen. Swollen airways don’t let as much air in or out of your lungs. Mucus production: During the attack, your body creates more mucus. This thick mucus clogs airways. When your airways get tighter, you make a sound called wheezing when you breathe, a noise your airways make when you breathe out. You might also hear an asthma attack called an exacerbation or a flare-up. It’s the term for when your asthma isn’t controlled.