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Food Sensitivity vs. Allergy vs. Intolerance

For each person who comes into my office, I ask myself: are your symptoms related to what you’re eating? It’s a simple question, but it’s actually quite challenging to determine. This article is going to focus on a common question I get asked: What’s the difference between a food sensitivity, allergy, and intolerance?

Note* in order to assess if your symptoms are related to what you’re eating, there are many factors at play like: what you’re NOT eating (ie. key nutrients), how much you’re eating, combination of what you’re eating, when you’re eating, the state of your nervous system when you’re eating, health of your microbiome, underlying medical conditions, medication or supplement side effects, etc. It’s not always just a food reaction.

Having an adverse reaction to food goes so much beyond experiencing unpleasant digestive symptoms. Think of eating fast food. There’s immense pleasure and satisfaction in the moment when you eat it, but how energetic do you feel after? I know I feel pretty sluggish and lazy afterwards.


Symptoms of Adverse Food Reactions

Heart burn or Reflux

Burping/Belching after a Meal

Feeling like food is ‘stuck’ in upper abdomen

Nausea or feeling unwell



Bowel Issues – constipation, diarrhea, urgency, floating stools, presence of mucous, etc.


Brain Fog

Migraines or Chronic Headaches

Joint Pain

Eczema/Skin Reactions

Weight gain

Mood Changes


Food Allergy vs. Food Sensitivity vs. Intolerance

Food allergies and sensitivities= your immune system over-reacting to food you’re eating. The protein component (antigen) in a particular food is seen as a foreign invader, so our immune system produces antibodies to neutralize and deal with it.

A food allergy is when this immune reaction happens immediately- within seconds to minutes after ingestion. IgE antibodies are produced, leading to histamine release and you get the classic symptoms of swelling, sneezing, rashes, and possibly, anaphylaxis. This can be more serious and these allergies are generally discovered earlier in life. Allergists do IgE food allergy testing.

A food sensitivity is a delayed immune reaction – hours to days after ingestion. A different antibody is produced – IgG antibodies, and these form little complexes with the protein (antigen) that can deposit in tissue and cause digestive symptoms or more subtle ones like migraines, fatigue, and weight gain. You can do a blood test for food sensitivity testing, where your blood is exposed to different food antigens and the antibody response is measured. This is something I do in practice, and some insurance companies cover the cost of testing. Read more here.

A food intolerance – generally refers to our inability to digest or handle a food. Lactose intolerance is the most widely known (and common) where gas, bloating, and diarrhea are the main symptoms after consuming dairy because of inadequate lactase enzyme. Another example would be histamine intolerance, where DAO enzyme is lacking or not working properly to help with the breakdown of histamine. You tend to get more swelling, rashes, headaches and digestive symptoms in this case. Reacting to chemical constituents like MSG, salicylates, alkaloids in nightshades, and FODMAPs could also be thrown into this category.

Tying it together:

Take dairy for example. Many people don’t feel the greatest after consuming it. So they switch to lactose-free, where the lactose sugar is removed. However, there are several proteins in dairy – whey, casein, albumin, and milk proteins, and these can cause an IgG immune-mediated food sensitivity, that is less obvious and immediate because it’s delayed, but can still impact how you feel.

How to figure it out:

1. Get support/ask for help: That’s where I can come in! During a thorough health history that explores symptoms, things you’ve tried, and assessing your dietary tracking, I can help determine the best starting place.

2. Elimination style diets – Have to be at least 4-6 weeks. This can be one food at a time or several at once- the important thing is the interpretation and awareness of how your symptoms have changed. Again, if you feel better after say wheat removal, that could mean you

3. FST Testing – this can provide an objective starting point because you get a report that tells you your degree of reactivity, which will direct you in terms of what foods to start eliminating, which to reduce, and which ones are ok to continue consuming.


Eating should be enjoyable, nourishing, and be a tool to optimize your health - not compromise it. Should you indulge in food sometimes that will make you feel briefly sub-par? Oh yes, that's soul food. But if you're consistently feeling unwell, book a Complimentary Consult or Initial Assessment here to explore the impact of food on your health.

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