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Allergy (0)

Definition of Allergies
Allergies are abnormal reactions to ordinarily harmless substances. The sensitizing substances, called allergens, may be inhaled, swallowed, or come into contact with the skin.

Allergens that most frequently cause problems are: pollens, mold spores, house dust mites, animal danders, foods, insect bites or stings, plants, insect spores, latex rubber, viruses, bacteria, medications and environmental conditions (such as cold temperatures). Allergic reactions can occur in one area, such as sneezing or a skin rash or sneezing, or may include more than one symptom.

Description of Allergies
Normally, the body learns to defend itself through experience - by encountering, battling and remembering one enemy after another. For decades, medical science has taken advantage of this ability by using vaccination to create immunity - the immunologic "memory" of a disease. Allergic reactions occur after the immune system mistakenly learns to recognize innocent foreign substances (allergens) as potentially harmful.

The following story illustrates how an allergy can develop:

Over a field of ragweed plants floats an invisible cloud of pollen grains, soon carried by the wind into a nearby town. The pollen is inhaled by a child whose body has never been exposed to this substance before.

Because of some genetic predisposing factor, this child's immune system overreacts and produces large numbers of IgE antibodies, all specially designed to respond to ragweed pollen. Several of the antibodies attach themselves to cells in the child's nasal passages and upper respiratory tract.

These cells (known as mast cells) contain strong chemicals called mediators, the best-known of which is histamine.

Later, when the child inhales the same kind of pollen again, proteins from the pollen bind in a lock-and-key fashion to the specially designed antibodies on the surface of the mast cells. This sets off an explosion of sorts, as the mediators burst from inside the mast cells, destroying the pollen and also damaging surrounding tissues. The results are sneezing, a stuffy head, sniffling, stuffed-up head and red, watery eyes - well-known hallmarks of allergies.