The immune system is a complex network of specialized organs and cells that helps defend your body against foreign invaders. When your body is exposed to outside elements like bacteria or viruses, your immune system produces protective antibodies and activated white blood cells to fight off these invaders.
An allergy (or allergic reaction) is when the immune system mistakes a harmless substance for dangerous one and produces an antibody called "immunoglobulin E", more commonly known as "IgE". IgE is an antibody that protects us from very specific parasitic infections, however, those of us that live in developed countries are not exposed to these parasites and IgE is usually absent (or present at very low levels) in people who do not suffer from allergies.
What Happens in an Allergy Attack?
When an allergic person is exposed to an allergen, IgE is produced to fight off the specific allergen. For example, if someone is allergic to cats and is exposed to a cat, then an "anti-cat" IgE antibody is produced. If the same person is also allergic to pollen and comes in contact with pollen grains, then an "anti-pollen" IgE antibody will also be produced and so on. Each allergen will have a specific IgE antibody to fight off that specific trigger.
Each time IgE is produced, the IgE molecules attach themselves to mast cells that are found in large numbers in the eyes, nose, lungs, intestines, and immediately beneath the skin. These mast cells contain many chemicals, including a substance called histamine which, when released into the body, can cause runny nose, sneezing, watery eyes, itching, hives, and wheezing. These effects are recognized as allergy symptoms.
When a sensitized person is exposed to an allergen, let's say a bee sting, then the bee sting allergen is trapped by the "anti-bee sting" IgE.
This trapping causes an immediate release of the chemicals from the mast cells, thus causing an allergic reaction.
In some cases, reactions can occur in several places throughout the body. Welts or hives may appear, spasm in the lungs may cause coughing or wheezing, the throat and tongue may swell; if anaphylaxis (severe allergic reaction) occurs, it may be fatal.
Can Allergies be Controlled?
Avoidance is the best defense against allergies. If you are unable to avoid the allergen (People with allergies must breathe, even when pollen counts are high!), medication may be taken to relieve symptoms. Medications may help relieve symptoms, but they do not alter the allergy immune response. If symptoms cannot be controlled or if someone is at risk of anaphylaxis (severe allergic reactions), allergy shots may be prescribed. Often people take allergy shots because they don't want to take medications every day. Allergy shots can put your allergies into remission.