Allergies, Intolerance Or Reaction? What is the difference?

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Allergies, Intolerance and Reaction – oh, my!

If you don’t know the difference between an allergy, an intolerance and a reaction, you are not alone. In many circles, the term “allergy” has been used as a catch-all phrase for all of these conditions. This has led to confusion regarding how to manage each correctly.

For a person to have an allergy, they must have an immune-system mediated reaction with the presence of allergen-specific antibodies. So, an allergy means that your immune system has started to create antibodies specific to a normally harmless substance, like pollen or a specific food. As a result, if you have an allergy, you should have IgE present in your body specific for the allergen.

Now, it can be tricky. Food allergy can involve the gastrointestinal tract, with symptoms like nausea, vomiting, diarrhea or constipation. This is where food intolerance can mimic food allergy, with a similar set of digestive disturbances.

However, they aren’t the same thing. If you have an intolerance, your body is unable to properly process a specific food or food component. Lactose intolerance is a common example. In this case, your body is unable to digest the lactose in milk because the required enzyme is absent or inactive.

As a result, the treatment is different than for food allergy. For lactose intolerance, a dose of the appropriate enzyme before the food is eaten can completely eliminate symptoms. This is not the same approach that you would take with an allergy. With a true allergy, a dose of an appropriate antihistamine before being exposed to the offending food would be the right approach.

Another distinguishing feature of food intolerance versus allergy is that intolerance may have a threshold dose. In other words, it would take a certain amount of the food in question to cause a problem. With food allergies an individual can be so sensitive that microscopic particles of the offending food will trigger a reaction.

With both food intolerance and food allergy, avoidance of the offending food will normally keep you symptom free. This is one of the reasons for the confusion of allergies with intolerances. In many cases, rather than get into a lengthy discussion, those with intolerances will simply call them allergies as well. “Allergy” seems to have more credibility than “intolerance”.  

The same confusion can occur between inhaled irritants and allergens when asthma is involved. You can actually have asthma without having allergies! This would be the case if you have a reaction to cigarette smoke rather than an allergy to cigarette smoke. Obviously, you should avoid smoking whether you are allergic to it or simply sensitive to it, especially if it is an asthma trigger.

However, there are differences in how you treat the symptoms. If you have a reaction but no allergy, antihistamine won’t help you. It’s possible, though, that you could need a puffer of steroid if inhaled irritants trigger asthma, but you won’t have another puffer to deliver antihistamine to the lungs. It won’t help.

Then there are reactions. The most common type of reaction is a adverse drug reaction. A reaction in this case refers to unwanted and negative effects of a specific drug. 

While some drug reactions are allergic in nature, many are caused by individual differences in how a drug is metabolized by a specific person. In addition, reactions can be the result of interactions between more than one drug, between the drug and a patient’s multiple disease conditions or between a drug and other substances like foods or herbs or vitamins ingested by the patient.

So, while you may have had a reaction to a specific drug, you may or may not be allergic to it.  If you are unsure, check with your medical professional.

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