Allergic diseases are among the major causes of illness and disability in the United States, affecting as many as 60 million Americans. An allergy is a specific reaction of the body’s immune system to a normally harmless substance, one that does not bother most people. People who have allergies often are sensitive to more than one substance.

Types of allergens that cause allergic reactions include pollens, house dust mites, mold spores, food, latex rubber, insect venom, and medications.

The respiratory symptoms of asthma, which affect approximately 17 million Americans, are often provoked by airborne allergens. Some people with allergy develop asthma, which can be a very serious condition. The symptoms of asthma include coughing, wheezing, and shortness of breath. The shortness of breath is due to a narrowing of the airways in the lungs and to excess mucus production and inflammation. Asthma can be disabling and sometimes fatal.