In 1906, Viennese pediatrician, Clemens von Pirquet, first coined the term “allergies" after he observed that certain symptoms of his patients might have been a response to outside allergens, like dust, pollen, or certain foods.

Signs and Symptoms

You know your allergies are starting if you experience swelling in parts of your body. This is called local or systemic inflammatory response, caused by the presence of allergens. For instance, if your allergies affect you in the nose, you will experience swelling of the nasal mucosa (allergic rhinitis). During this condition, you will probably find yourself performing the “nasal salute" more than necessary as itching of your nose will induce you to wipe your nose in an upward direction.

On the other hand, if the allergies hit you in the eyes, redness and itching of the conjunctiva often follows. Other common signs of allergies are wheezing and dyspnoea, bronchoconstriction, and sometimes outright attacks of asthma. You may also experience various rashes, such as eczema, hives, and contact dermatitis.

Systemic allergic responses are more serious compared to local symptoms. Depending on the severity of your response, allergies can cause cutaenous reactions, bronchoconstriction, edema, hypotension, coma, and even death.

Hay fever is actually one example of minor allergies caused by airborne pollen. But aside from environmental factors, allergies may also be triggered by medications.

Why do we get allergies?

Our immune system is a well-trained and disciplined bio-weapon that protects our bodies from harmful substances. Its mechanics is so amazing that it can identify and destroy many foreign invaders. However, as amazing as our immune system is, it makes mistakes sometimes. And so we have allergies, which, as we mentioned, results from a hypersensitive immune system.

The hypersensitized immune system misidentifies an otherwise innocuous substance as harmful, and then attacks the substance with a degree of ferocity that is greater than required. As a result, we experience problems that can range from mildly inconvenient to uncomfortable to total failure of major organs of the body.

How does the immune system go into a hypersensitized state?

There are actually several ideas on this. Some schools premise that allergies are almost always triggered by protein. Certain persons have faulty genetic codes so that their lymphocytes or the white blood cells (the stuff that your immune system is made of) are unable to property distinguish between the threatening and the non-threatening proteins.

So, for example, when you ingest protein from shellfish, your lymphocytes think that the substance is trying to invade the body. As a result, they produce large amounts of antibodies which attach themselves to mast cells and basophils throughout the body. This is known as the sensitizing exposure and this is the very reason why you suddenly develop allergies.

More information can be found in http://www.health-00.info