The lining of the airways swells from inflammation, which causes an increase in mucus that blocks the airways. Because it’s more difficult to breathe out than to breathe in, more air is retained in the air sacs in the lungs with each breath. Someone having an asthma attack may feel as though he or she is breathing through a narrow straw or, in the case of a severe attack, may even have the feeling of near suffocation.The changes that take place in the lungs of asthmatic persons make the airways hyper-reactive to many different types of stimuli that don’t affect healthy lungs. In an asthma attack, the muscle tissue in the walls of bronchi goes into spasm, and the cells lining the airways swell and secrete mucus into the air spaces. Both these actions cause the bronchi to become narrowed (broncho-constriction). As a result, an asthmatic person has to make a much greater effort to breathe in air and to expel it.Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscle to contract and stimulate mucus formation. These substances, which include histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area, which is a key part of the inflammatory response. Many patients with asthma are prone to react to such "foreign" substances as pollen, house dust mites, or animal dander, these are also called allergens.An asthma attack is characterized by difficulty in breathing, periodic attacks of wheezing, shortness of breath, and a tight feeling in the chest. A cough producing sticky mucus is symptomatic. The symptoms often appear to be caused by the body’s reaction to a trigger such as an allergen (commonly pollen, house dust, and animal dander), certain drugs, an irritant (such as cigarette smoke or workplace chemicals), exercise, or emotional stress.