Bronchodilators are medications commonly used by people with asthma. They relax the muscles that surround the airways and allow the airways (the tubes that carry air into and out of the lungs) to open up. Some bronchodilators act quickly to stop asthma symptoms (such as wheezing, coughing, or shortness of breath) that are often caused by narrowed airways. Known as rescue, quick-relief, or fast-acting medications, these bronchodilators are meant to be used when a person first notices symptoms, but their effect doesn't last long. Other bronchodilators, known as controller medications, are longer acting and are used to control, or prevent, asthma symptoms.