What’s the difference between food allergy, sensitivity, and intolerance?

Thanks to Mélanie DesChâtelets, ND for co-authoring this post!

Do you ever feel confused about the difference between food sensitivity, food allergy and food intolerance? The differences are actually pretty simple to understand and will help you understand how food affects you. First, some basic definitions:

Antibody: A large Y-shaped protein produced by the immune system.  Its job is to recognize foreign proteins and neutralize them.  It’s what happens when you get a cold, the bacteria or virus is recognized and then neutralized by antibodies.

Enzyme: In simple terms enzymes help breakdown things.  Enzymes are very specific for what they break down. Therefore, your body has thousands of different enzymes to break down very specific compounds.  Without enzymes the process may not occur at all or at a very reduced rate. In the digestive system, enzymes help break down food into smaller units for absorption.

Both food allergy and food sensitivity are antibody-mediated reactions to food.  The antibody recognizes a food protein as harmful and tries to neutralize it.  If this is similar then what is different? We have different types of antibodies in our body.  Different types of antibodies react differently and cause different symptoms.

Food allergy

Food allergy is mediated by an antibody called IgE.  When this type of antibody reacts with a foreign protein it immediately elicits typical reactions ranging from uncomfortable to life threatening.  Skin irritation, redness, and swelling are common.  Difficulty breathing is more disturbing as it represents tightening of the airway.  Other symptoms such as hoarseness of voice, stuffy and runny nose, itchy and red eyes as well as nausea and vomiting can are also seen with food allergies.

Food allergy

Food allergy

Here’s a diagram – imagine the pink line represents the symptom threshold; when you cross this line you have symptoms.  The star represents ingestion of the allergic food item.

With food allergy, as soon as the offending food is ingested, IgE levels rise and react quickly.  The allergic symptom threshold is always reached. Avoidance of this offending food is necessary as it can be life threatening.  The levels of IgE will also drop relatively quickly and within 5-7 days you typically no longer have symptoms.

Food sensitivity

Food sensitivity is mediated by an antibody called IgG.  IgG antibodies react very differently from IgE.  When IgG antibodies react with foreign proteins, they elicit a milder, slower, and non-typical reaction.  Symptoms can vary from migraines, to increased behavioural difficulties in children with ADHD, to chronic digestive concerns (constipation, diarrhea, IBS, IBD), decreases in energy, skin issues (acne, eczema), and other vague symptoms.  Here’s the problem – unlike food allergies, food sensitivities are very hard to diagnose.  This is because their impacts can be seen 24 to 48 hours after the ingestion of the offending food.  There are two ways that can help identify food sensitivities: the first is a strategic elimination/hypoallergenic diet, which works as both a diagnostic tool (to identify offending foods) and treatment (avoidance of offending foods as a first step towards long-term healing). The other is an IgG food sensitivity blood test – I offer this testing via either Immunolabs or Rocky Mountain Analytical. This tests how reactive your IgG antibodies are against various foods.  The higher the reactivity the higher likelihood a food sensitivity might be present.  This test can be a good starting point in assessing potential food sensitivity.

Food sensitivity

Food sensitivity

Here’s a diagram to demonstrate how IgG works.

With food sensitivity, the offending food is ingested and the IgG antibody levels rise slowly and linger for up to 3 weeks.  This is what makes a food sensitivity so hard to diagnose.  You first ingest the offending food sensitivity and you are symptom-free.  This is because you are still far from your symptomatic threshold.  In a few days you ingest this same food item and again no symptoms.  What you don’t know is that your IgG antibody levels have accumulated with those of your last exposure.  Third time is a charm, you ingest the food and this time you get symptoms, such as migraine, constipation, weight gain, water retention, skin breakouts, fatigue, etc.  Please note in this example I used 3 days but this is for illustrative purposes and is not literal. It can be confusing! Symptoms don’t appear immediately, so it is hard to link exposure to symptoms and you are left guessing at which foods is causing symptoms.  Unlike an IgE food allergy were every single exposure is followed by symptoms, IgG food sensitivities depends on frequency and dose of the exposure.

Food intolerance

Food intolerance

Food intolerance

Food intolerance represents an enzyme deficiency, meaning your body can’t break down a component of food and this causes digestive upset. The most obvious example is lactose intolerance or lactase enzyme deficiency.  This enzyme is important in breaking down lactose found in dairy products.  The lack of this enzymes results in gas, diarrhea, and discomfort.

I work with many patients to address food sensitivities. The goal is not to eliminate a food for the rest of your life although avoidance for a period of time is sometimes necessary while we improve the integrity of the gut lining so that you can once again tolerate the offending food.  When you figure out which foods you are sensitive to and understand the symptoms, you are empowered to take charge of your health!

This post was co-authored with Mélanie DesChâtelets, ND.


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