Experts aren’t sure why some people get asthma, while others do not. It’s possibly caused by a combination of environmental and inherited (genetic) factors. It is known that exposure to certain kinds of substances (allergens) can trigger allergies. These differ from person to person. Some common asthma triggers include: pollen, dust mites, mold, pet hair, respiratory infections, physical activity, cold air, smoke, some medications such as beta blockers and aspirin, stress, sulfites and preservatives added to some foods and beverages, and gastroesophageal reflux disease (GERD).