Common asthma triggers and potential causes Asthma, a chronic lung disease that results in inflamed and narrowed air passages, affects millions of people around the world. The National Heart, Lung and Blood Institute notes that more than 25 million people in the United States have asthma. Asthma is also prevalent in Canada, where the Asthma Society of Canada says more than three million people currently have asthma. When airways narrow and swell, they can produce extra mucus. Breathing becomes quite difficult when asthma is present. The Mayo Clinic says that asthma is just a minor nuisance for some people, while others may experience life-threatening attacks. Recognizing potential triggers and avoiding them can help control symptoms. The changing of seasons can be a tricky time for asthma sufferers because of the increase in air irritants. Pollen and mold spores are known asthma triggers. Spring cleaning around the house also may trigger an attack if dust, pet dander or particles of cockroach waste are stirred up. People who are allergic to certain substances also may discover these same allergens can trigger asthma attacks. Irritants in the environment also can bring on such attacks. The Asthma & Allergy Foundation of America indicates that, while people may not be allergic to certain irritants, irritants can bother inflamed and sensitive airways. Cigarette smoke, wood fires, charcoal grills, smog, strong fumes, and chemicals also may trigger asthma attacks. People with asthma also must take care when exercising or when they develop respiratory illnesses. Exercise-induced bronchoconstriction can appear after several minutes of sustained exercise. The AAFA also notes that colds, flu and sinus infections are among the most common asthma triggers in children. Although many asthma triggers are known, researchers continue to explore what causes asthma. The NHLBI says that people may be more likely to develop asthma if: • They have atopy, an inherited tendency to develop allergies. • Their parents have asthma . • They were exposed to certain respiratory infections during their childhood. • They had contact with allergens while their immune systems were developing. A theory known as the “hygiene hypothesis” suggests another potential cause for asthma. Researchers say that growing concerns with hygiene and sanitation have removed many of the types of environmental exposures that once helped children develop strong immune systems. As a result, an increased risk for atopy and asthma has surfaced. Asthma sufferers can try to avoid common triggers and may find that medication and other lifestyle changes can help control their symptoms. CAPTION: Various triggers can stir up asthma symptoms.