Asthma is a disease that affects the airways in the lungs, making them inflamed and swollen. The inflammation makes airways more likely to be bothered by allergy triggers and things such as smoke, stress, exercise or cold air. Airway muscle spasms block the flow of air to the lungs, causing symptoms that may include difficulty breathing, a tight feeling in the chest, coughing and wheezing. Sometimes the only symptom is a chronic cough, especially at night, after exercise or when laughing. Asthma may have only mild symptoms, or it can be life-threatening when attacks stop breathing altogether.