Asthma symptoms include wheezing, which is a whistling or squeaky sound that occurs when a person breathes. Wheezing is caused by the narrowing of the airways due to inflammation and excessive mucus production. It is a common symptom of asthma and can be heard during both inhalation and exhalation. Wheezing is often accompanied by other asthma symptoms such as shortness of breath, chest tightness, and coughing.