What is an Allergy?

For unknown reasons, a person with allergies overreacts to a substance that is harmless to most people. The most common of these substances, or allergens, are airborne materials such as pollen and dust. A person without allergies simply swallows or coughs out these substances. But the immune system of a person with allergies reacts to them by making disease-fighting proteins called antibodies.

The antibodies cling to various body cells, where they await future attacks. The next time the person inhales the allergen, the waiting antibodies cause the cells to release irritating chemicals like histamine. These irritants migrate to the breathing passages, where they cause the familiar unpleasant symptoms.