http://www.aafa.org/display.cfm?id=8&cont=6 Asthma and Allergy Foundation of America http://www.aafa.org/display.cfm?id=8&cont=6 "Asthma: What Causes Asthma" science claims Asthma and Allergy Foundation of America Asthma and Allergy Foundation of America "Asthma: What Causes Asthma" http://www.aafa.org/display.cfm?id=8&cont=6