One of the marvels of the human body is that it can defend itself against harmful invaders such as viruses or bacteria. But sometimes these defenses are too aggressive, and harmless substances such as dust mites, mold or pollen are mistakenly identified as dangerous.
Allergies are these overly aggressive or abnormal responses by our immune system to an otherwise benign material. This normally harmless substance (pollen, dust mites, cockroach, mold, animal dander, etc) is called an allergen.
When people with allergies come in contact with one of these allergens their immune system releases chemicals to combat this "invader." It is these chemicals that cause a variety of allergy symptoms.
It is estimated that 50 million Americans—about one in five-- suffer with allergies.