Asthma symptoms occur when airway muscle spasms block the flow of air to the lungs and/or the linings of the bronchial tubes become inflamed. Excess mucus may clog the airways. An asthma attack is characterized by labored or restricted breathing, a tight feeling in the chest, coughing and/or wheezing. Sometimes a chronic cough is the only symptom. Asthma trouble can cause only mild discomfort or it can cause life-threatening attacks in which breathing stops altogether.