Asthma triggers are exposures that cause or worsen asthma symptoms. Indoor asthma triggers include allergens, airborne non-allergenic particles, and various gaseous air pollutants. Tobacco smoke, which contains particles and many gaseous pollutants is an important asthma trigger. Allergens from house dust mites, pets, molds, cockroaches, rodents, and plants such as grasses, weeds, and trees can trigger asthma, these allergens are present in particles too small to see. Particles as well as gaseous pollutants, such as ozone, from outdoor air can trigger asthma. Various chemicals found in workplace air can also trigger asthma. Air pollutants are not the only triggers for asthma. Other important asthma triggers include exercise, cold air, stress, and respiratory infections. Sources of additional information include:
a web site from the U.S. Environmental Protection Agency;
a web site from the Centers for Disease Control and Prevention;
the section of this web site on dampness and mold;
the section of this web site on volatile organic compounds.