The airways are lined with a type of muscle called smooth muscle. In people with asthma, these muscles often tighten in reaction to things like allergies, cold weather, or smoke. When this happens, the airways become narrower, blocking the flow of air and making it harder to breathe. This narrowing of the airways is known as bronchoconstriction.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995-2016 The Nemours Foundation/KidsHealth. All rights reserved.