A hand holds a wok with stir fry ingredients flipping about it.

Food Allergies vs. Food Sensitivities

In the confines of the eczema realm, food is usually seen as one of the triggers of our struggles. And when it is, the imperative question pops up: How do I know which foods?

Food allergy testing

Like myself, I am sure many eczema sufferers first think only of food allergy testing. That is where we are normally steered first. If so, there are many ways to do food allergy testing:1

  • Scratch test
  • Blood draw
  • Patch test

Scratch testing

A one-stop-shop where the allergist scratches your skin with many different elements (for this purpose, food), and within a few minutes, the skin will show what is highly reactive, semi-reactive, and non-reactive. Usually, a hive will pop up if you are allergic to a certain food. It is a cheaper route to take, as well, to find out an allergy.

Blood draw

Instead of scratching the skin with the potential allergy, we simply draw blood and measure the IgE antibodies specific to certain foods. Sometimes, these blood tests are used for more severe cases since they are safer and do not cause anaphylaxis. However, they can also draw false positives or false negatives.1 For example, my sister is highly allergic to shellfish. She did a blood draw a few months ago, and it came back that she should be able to eat shellfish again. Skeptical, my father had another test done, and it came back as highly allergic, once again, to shellfish. So, if you feel there is a serious matter, do at least two types of allergy tests to make sure.

Patch testing

This type of test requires patience and is involved in delayed allergic reactions. It is usually a four-day process, sometimes five. Patches of the substances being tested are placed on your back. You must wait a period of time (usually 48 hours) before you go back to your doctor to have the patches removed. Then, another 24 hours pass before they are able to do an actual reading.

Food sensitivities and intolerances

Besides food allergies, there are two other food-related woes we should be aware of in our journey for answers: Food sensitivity and food intolerance.

Now, do not confuse the two. One is very different from the other, and they are both different from allergy testing. Most of the time, people use these interchangeably, which is incorrect.

Food intolerance

First off, a food intolerance has nothing to do with our immune system. You can still get symptoms, but it is not immune-related. It is why we have things like lactose intolerance. The body isn't allergic to lactose or dairy-type products, but it lacks the enzymes to break it down in the gut.1

Food sensitivity

The immune system comes into play when it comes to food sensitivity (however, a bit differently than an allergy).

What's the difference?

Food sensitivities can affect many parts of the body and can either show up within an hour of eating said food or even days later. An allergy would mean our skin, breathing pathways, and gut would be affected, often right after eating said food. Allergies are much more serious and can mean life or death if the allergy is that extreme.

As per population, more people tend to have food sensitivities than allergies. Also, a small or large amount of food may be needed to trigger a food sensitivity, while a food allergy only needs one molecule to trigger a reaction.

Last but certainly not least, the mechanism that creates these immune responses is different. For a proper allergy, it's your IgE (Immunoglobulin E: a specific antibody in your system). For a food sensitivity, it's your white blood cells plus other antibodies like IgG (Immunoglobulin G) and IgM (Immunoglobulin M).2,3

Food sensitivity tests - IgG vs MRT

We now know IgG plays a role in food sensitivity. However, there is a caveat. Most food sensitivity tests being peddled around (ones you see advertised) measure your IgG levels. Sounds accurate, right? Not totally.


IgG is a 'triggering mechanism' that activates white blood cells, which releases interleukins (a cytokine essential in activating immune cells), TNF alpha (an inflammatory cytokine that causes symptoms of many autoimmune diseases), and more. These are the dudes that cause a ruckus — the more that are released, the more issues. In turn, that means that measuring IgG isn't sufficient in getting to the bottom of what foods are causing a sensitivity. What needs to be tested are these very interleukins and TNF alpha.1,2,3


Cue, MRT. MRT = Mediator Release Test. This test identifies those interleukins and TNF alpha. That way, you are getting a more accurate test. I will go out on a limb and say they are generally more expensive (mine was), but accuracy means more to me than saving money when it comes to needed answers.3

Why do food sensitivities matter?

Again, they are not allergies. But, when your immune system is on overload (like a cup spilling over), food can play a major role in balancing this. Our diet matters, especially since a good chunk of our immune system is in our gut. Knowing which foods you may need to avoid for a few months can help level out your cup and get you back on track to a healthier, happier you.4

Bear in mind a lot of the things that make your cup overflow aren't just foods. It's things like stress, medications, lack of sleep, etc. Our body works as a whole. Treat it as one.

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