The term allergy is tossed around a lot these days. However, it’s important to understand that not every reaction to a food or substance is an allergy.

To have an allergy, you must have an abnormal immune system reaction to a generally harmless substance. The body tries to protect itself from this substance by producing a type of antibody called immunoglobulin E (IgE). This type of antibody causes mast cells to create a cocktail of chemicals to defend against the substance.

What this really means is that your immune system has identified a substance as an invader, when it actually isn’t. This differs from abnormal side effects of a drug, for instance. Most drug reactions occur as a result of your body’s metabolism of the drug, and not because of an immune system response.

The proper targets of your immune system are bacteria and viruses, not the bouquet of roses on your kitchen table. However, when you have allergies, your immune system will react by releasing specific chemicals that create the allergic symptoms. One of the first “early” reactive chemicals is histamine. As the reaction progresses, other chemicals are released, including leukotrienes (pronounced loo-ko-tri-eenz). Obviously, the most common allergy drugs are antihistamines that help to counteract the body’s initial histamine reaction. 

If you don’t know what leukotrienes are, you are not alone. These are another class of chemicals that are responsible for allergic inflammation in the body. They work differently than histamines, and can be part of the reason your allergies may not respond well to standard antihistamine treatment, particularly if you are chronically exposed to your allergen.

We are all familiar with the standard allergic constellation of irritated eyes, runny nose, stuffed sinuses, post nasal drip, cough and itchy or sore throat. However, did you know that you could even have itchiness in the ears or a buzzing sound as part of your allergic symptoms?

And allergies don’t just stop with the eyes, ears, nose and throat; you can experience symptoms from your nose to your toes, including hives and other skin conditions, gastrointestinal problems and such vague problems as fatigue, headaches, loss of smell and sleep issues. So just because your nose doesn’t run, don’t count out allergy.

Allergy reactions can be classified as mild, moderate or severe:

• Mild reactions typically include rash and eyes that itch or water as well as nasal discharge and congestion. Note that all of these symptoms are local to the site of exposure to the allergen, and do not spread to other parts of the body.

• Moderate reactions are characterized by symptoms that can spread to other parts of the body, including itchiness, rash or breathing difficulties. So, the allergic reaction is no longer localized.

• Anaphylaxis is the most severe type of reaction. Symptoms can range from constriction of the throat and breathing passages, to nausea and vomiting as well as circulatory problems that can result in extremely low blood pressure, dizziness, shock and loss of consciousness. If you ever have this kind of allergic reaction, each subsequent one is likely to be more severe and more dangerous. 

Here’s a little known fact: you cannot be allergic to a substance that you have never been exposed to. In order for an allergic reaction to take place, your body must have already created allergic antibodies, known as IgE, for that specific substance. The creation of IgE is called sensitization to the substance and can only occur if you have been exposed to enough of the allergen to create the allergic antibodies.

It doesn’t take a lot of exposure to develop an allergy, but it always requires at least some!

Once the body is sensitized, the typical allergic symptoms will then take place when you are exposed to it. These symptoms can vary depending on the allergen itself and the kind of exposure. For instance, you may have different allergic symptoms for airborne irritants than for a food allergy.

Just because you’ve always eaten a certain food, or never had seasonal allergies before, doesn’t mean that you can’t or won’t develop allergies in the future. Medical researchers are unclear why some people develop allergies over time and others don’t.  However, the development of allergies is most common in children and young adults.

In general, if you’ve made it into your 20’s or 30’s without allergies, you are less likely to develop them later. But don’t count them out: approximately 40% of North Americans are living with allergies, which means more than 1 in 3 of us will deal with them sometime in our lives.