It seems as if everyone has a food allergy. The truth is most of those who think they have a food allergy really have a food intolerance. What’s the difference?

Food allergy

An allergy is a reaction by the body’s immune system. Something that should be ignored, isn’t. The body overreacts with an outpouring of chemicals that trigger itchy eyes, runny nose and sneezing or coughing if the allergen is inhaled. If it’s eaten, the reaction tends to be mainly nausea, vomiting and diarrhea. In either situation there is a risk of developing hives and becoming short of breath.

Only an allergic reaction can progress all the way to anaphylactic shock, a life threatening situation where the blood pressure drops precipitously and the airway can close in. Allergies can kill. The most common triggers: shellfish, milk, peanuts, tree nuts and fin fish.

Food intolerance

A food intolerance is rarely, if ever, life threatening — although you can feel very sick. In this situation, the body is unable to tolerate a specific substance. The stomach and intestines rebel. Lactose intolerance is a perfect example. As we age the amount of lactase, an enzyme that lives in our gut and helps us to digest the milk sugar lactose, drops. In some people it disappears completely.

The result is that lactose cannot be digested by the person. The bugs that normally live in our intestines have a food bonanza. The lactose that would normally be digested and absorbed by the gut before it gets to them isn’t and so they get it all. The result for the poor person is severe tummy cramps, nausea, vomiting and diarrhea if they drink milk or eat any dairy with the lactose still there. That’s an intolerance.

Why is it important to know the difference?

Because one can kill (the allergy) and that means you need to avoid the trigger and perhaps always have an adrenalin / epinephrine auto-injector with you.

What’s interesting is that a recent study published in JAMA (Journal of the American Medical Association) found that only about half the people who think they have a food allergy actually do, the rest actually have an intolerance. You can understand how important it is to know which one you have. If in doubt, speak to your doc and if necessary you can be tested, but this should be done carefully and in a controlled environment because if you do have an allergy it can become serious quickly and so someone needs to be there at your side with the necessary expertise.

Dr. Mitch Shulman is an Assistant Professor, Dept. of Surgery, McGill Medical School and an Attending Physician, Emergency Department, McGill University Health Centre. He’s also the CJAD AM 800 Medical Consultant.

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