Wheezing is a whistling sound that occurs during breathing, usually during expiration (breathing air out of the lungs) through narrowed airways. Inflammation of the airways, bronchospasm (tightening of the muscles around the bronchial tubes), and hypersensitivity (reactivity to triggers such as allergens, irritants, or infections) all play a role in the development of wheezing. Any conditions or diseases that can constrict the airways can lead to wheezing. Wheezing can be accompanied by other symptoms such as coughing and shortness of breath. Wheezing may also occur in anaphylaxis, a severe and potentially life-threatening allergic reaction.