Bronchospasm is caused by the release (degranulation) of substances from mast cells or basophils under the influence of anaphylatoxins. The overactivity of the bronchioles’ muscle is a result of exposure to a stimulus which under normal circumstances would cause little or no response. The resulting constriction and inflammation causes a narrowing of the airways and an increase in mucus production; this reduces the amount of oxygen that is available to the individual causing breathlessness, coughing and hypoxia.