As a child there were many things that I was allergic to. I remember doing the RAST skin test in the doctor’s office and learning that I was allergic to grass and some trees, dust (who isn’t allergic to dust), and many other things I wasn’t worried about because I didn’t come into contact with them regularly. It wasn’t until I was an adult that I realized the difference between allergies and sensitivities, specifically when it relates to food. Being able to understand the immune difference took several conversations, articles, and explanations but now I’ve got it and I want to explain it to you.
An Intro to the Immune System
In order to understand the response to food allergies and sensitivities, you must first be introduced to how the immune system works (the immune system is far more complex than this little introduction, however this is a smidgen of what is going on). The job of the immune system is to determine what is part of you and what is an outside “invader” that need to be attacked. Recent research indicates that 70% of the immune system is in the GI tract, which makes sense because this is the area of the body where foreign objects (food) are introduced on a regular basis.
The immune system has several layers which can respond to a foreign body. For the sake of discussion of food allergies and sensitivities, we will discuss only the parts of the immune system that surround these.
- The innate immune system is the first line of defense against things that your body is unsure of. It responds quickly to deal with a threat such as bacteria, viruses, parasites, yeast, mold, or mildew. In response to these threats the immune system will produce T-helper 1 cells such as mast cells, phagocytes, killer cells, among many others to deal with the threat without having to call out the other immune fighters out. If this were a bar fight, the innate immune system would be the friends of the fighters pulling them apart with out letting it get out of hand.
- The adaptive immune system is the next layer of immune response, which is slower in response. This part of the immune system deals with antibodies (AKA immunoglobulins or Ig) and antigens (the foreign invader). The antibodies are proteins that are produced by the immune system in response to the allergy trigger, an antigen (the threat). The antibody will attach to the antigen to “flag” it, then the immune system can destroy the antigen. There are different types of antibodies (immunoglobulins, Ig), each with a differing role in what they will attack.
- IgA antibodies-protect parts of the body that are exposed to the outside-eyes, ears, nose, lungs, digestive tract, vagina
- IgM antibodies-found in blood and lymph fluid; they are the first antibodies released to fight; they are temporary lasting about 3 months until the IgG antibodies are released
- IgG antibodies-they are found in all body fluids and are the most common; these IgG antibodies continue to be produced as long as the foreign substance that is challenging the immune system are around
- IgE antibodies-found in the lungs, skin, and mucous membranes; these antibodies are produced quickly within a few minutes to a couple of hours when the body finds something offensive
These antibodies all attack a little differently. IgA, IgM, and IgG antibodies are triggered in response to foods, food chemicals, environmental chemicals, and toxins produced by bacteria in the body. The antibodies may take several days to be made and thus these reactions are called delayed hypersensitivity reactions. In the sense of food, you may exposed to an almond on Monday, yet not have the antibodies to it until Wednesday or Thursday. On the other hand, IgE antibodies can be created within a matter of minutes.
Food Allergy vs. Food Sensitivity Testing
The difference between a food allergy vs. food sensitivity is the way the body responds; which kind of antibodies are produced. If the body determines a food is a threat it will create an antibody to defend it. The production of IgE antibodies is what is typically considered a “true” allergy. These typically happen quickly, within a few minutes to a few hours and are usually obvious in presentation. The IgA, IgM, and IgG antibodies are linked to sensitivities. These sensitivities take several days to present, they are less obvious in their presentation and can be difficult to diagnose without blood testing. When testing is done, you have to consider what antibodies are being tested. If IgE antibodies are tested, it will only pick up allergies, where if IgG (most common), IgA, or IgM antibodies are tested, it would be looking for more of the delayed response, or sensitivity.
While blood testing for allergies and sensitivities are often used they are not 100% accurate. They can give you an idea of which foods are causing problematic responses. However, doing an elimination diet may also yield results that you are looking for. Elimination diets are actually the gold standard to find offensive foods, however blood testing may be more beneficial if you need to see it written on paper before you start doing your testing.