Allergic Reactions Are Complex And Can Be Dangerous

Unless your immune system has been compromised, the body fights back very effectively when a substance the body identifies as "foreign" enters.

These foreign substances are called antigens. When the body detects one, the immune system manufactures specific antibodies that attach to and neutralize the antigen; however, for those with allergies, a normally harmless substance such as grass pollen, peanuts, or wasp venom can cause an immune response that results in what we know as allergy symptoms.

"Normal" Allergic Reactions

Antigens that cause allergic reactions are known as allergens. The first time an allergy-prone person is exposed to an allergen, he or she makes large amounts of the antibody that corresponds to it. This will be a form of the IgE (immunoglobulin E) antibody. Each IgE antibody is allergen specific; for example, one reacts against grass pollens, another against ragweed.

These IgE molecules attach to the surfaces of mast cells (in tissue) and basophils (in the blood). Mast cells are plentiful in the lungs, skin, tongue, and linings of the nose and intestinal tract. When IgE antibodies sitting on a mast cell or basophil are “cross-linked” by their specific allergen, the mast cell or basophil release the powerful chemicals stored within their granules. These chemical mediators, including histamine, cause the allergy symptoms such as wheezing, sneezing, runny eyes and itching. The great majority of allergic reactions are limited in severity and usually just a minor inconvenience.

Unusual Allergic Reactions -- Anaphylactic Shock

Allergens can also produce anaphylactic shock, a life-threatening allergic reaction characterized by swelling of body tissues, including the throat, and a sudden drop in blood pressure.

What We've Learned

This, then, is the essence of an allergic reaction - cells in the body releasing histamine and other chemicals which then cause the symptoms we know as allergic reactions.

For example, histamine released in the nose, eyes, and sinuses, stimulates sneezing, a runny nose, and itchy eyes.

When released in the lungs, histamine causes narrowing and swelling of the lining of the airways and the secretion of thick mucus.

When released in the skin, it causes rashes and hives.

And in the digestive system, it causes stomach cramps and diarrhea.