Our immune systems work to protect us against foreign substances that could harm us, such as bacteria or viruses. But what happens when the immune system reacts to a harmless substance, such as pollen or dust, setting off physical symptoms that include sneezing, watery eyes, congestion, hives or even anaphylactic shock?

It means we have an allergy.

The word allergy comes from the Greek "allos", meaning change, and ergon, meaning reaction. Coined in 1906 by Viennese pediatrician Baron Clemens von Pirquet, the word allergy has come to mean a physical reaction to an external substance introduced into the body.

If we are hypersensitive to an allergen, we have an allergy. An allergen can be any substance that causes allergic reaction, the most common being pollen, ragweed, pet dander, insect stings or bites, mold spores, and foods. This is by no means a complete list, as allergens can also include such substances as latex or dust mites.

Why do some people have allergies and not others? Why does the family pet cause one family member to sneeze and suffer watery eyes, but has no effect on the rest of the family? Heredity does play a part; if one or both parents have allergies, the chances increase of passing it on. But exactly what causes one person to be allergic and not another, even within families, is not yet known.

Though we don't know why some people are allergic and others are not, we do know the process an allergic reaction follows.

First, there must be an exposure to the allergen. Assume the allergen is pet dander. This first contact rarely results in the symptoms associated with a reaction. Rather, this is when the immune system is put on alert to pet dander. The allergic person is now sensitized to that allergen.

The pet dander enters the body after initial exposure. The immune system responds to the foreign substance, and sends out antibodies to eliminate the dander. The immune system, though, overreacts, sending out the antibody IgE in abundance. It is this overreaction to otherwise harmless substances that defines an allergy. The Ige irritates certain cells, which then release histamine, and the allergic reaction becomes evident. We sneeze. Our eyes water. We're congested. We break out in a rash.

Allergy sufferers have numerous remedies available to them, and many can be obtained over the counter. These medicines are commonly referred to as anti-histamines and treat the symptoms; there is no cure for allergies.

The common symptoms caused by allergies can be annoying, disruptive, and, at times, severe enough to demand more extensive treatment such as prescribed medication and bed rest. The most severe reaction is anaphylactic shock, which is life threatening and is treated with an adrenaline injection.

Allergic reactions vary from person to person, and can take the form of such diseases as asthma, eczema, and hay fever. However an allergy manifests itself, the symptoms should not be ignored, and a physician consulted when symptoms appear.

Learn more about this author, Shelly Mcrae.
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