Asthma is a condition in which your airways narrow and swell and may produce extra mucus. This can make breathing difficult and trigger coughing, a whistling sound (wheezing) when you breathe out and shortness of breath. The most common symptom of asthma is wheezing Other asthma symptoms may include: coughing, especially at night, when laughing, or during exercise tightness in the chest shortness of breath anxiousness or panic fatigue