What causes an allergy?
An allergic person produces a specific type of antibody called immunoglobulin E, or IgE, in response to normally harmless substances such as certain foods or medicines, pollen, animal dander and mold. These IgE antibodies cause allergic reactions. If a person is exposed again to the allergen, the IgE antibodies stimulate what are called mast cells to release chemicals such as histamine to destroy the “foreign” substance.
The release of histamine causes typical allergy symptoms such as runny nose, itchy and watery eyes, sneezing, asthmatic reactions, hives, and a drop in blood pressure in severe cases. This is why antihistamines are the mainstay of treatment for allergies.