In food allergy, the immune system is like a playground. The balance of allergy and immune tolerance is like a see-saw. Food allergy is not just the activation of allergy cells by a food. Food allergy is the lack of tolerance to a food. It’s important to understand allergy versus immune tolerance. Read on to learn how!
This article was originally published in 2020 and has since been updated!
The Balance of Allergy and Tolerance
When I think of allergy, I think of two parts of the immune system: allergy and tolerance.
The Immunology of Allergy
Allergy is what you may think of as what should NOT be the body’s default response to a food. You would be right! An allergic response is one in which the immune system, whose purpose is to protect us from infection, senses the food is an evil-doer so attacks it. Why would the immune system get confused like this? Peanuts are not evil-doing infections, so why would our immune systems make such a mistake? Researchers are working hard to determine WHY kiddos are developing food allergies.
How an allergic reaction occur
What we do know is that allergy cells become activated when a baby with a peanut allergy consumes peanut protein. The key allergy cells in allergic reactions are mast cells. In peanut allergy, mast cells are activated because they have peanut-specific allergy antibodies on their surfaces. The antibodies are also called peanut immunoglobulin E (IgE). Peanut IgE is like a lock on a door, and peanut protein is the specific key that opens that lock. Once the peanut “key” unlocks the mast cell “door,” the mast cells release chemicals. These chemicals, such as histamine, then cause the allergic reaction.
The Immunology of Tolerance
Tolerance is what you may think of as what should be the body’s default response to a food. Again, you would be right! When a baby is given a food for the first time, we expect the baby’s immune system will tolerate it. We do NOT expect an allergic reaction. Tolerance is a complex process involving multiple components of the immune system, and I won’t get into those nitty-gritty details. The result of tolerance is that a baby is able to eat the food without allergy cells being activated. Tolerance can occur even if a kiddo has allergic antibodies to the food.
We’ve talked about allergy. We’ve talked about tolerance. So how do these two interact? And we can test for allergy, but how do we test for tolerance?
The Interactivity of Allergy and Tolerance
We (allergists) do not know why a kiddo develops a food allergy. What we do know is that early introduction and regular consumption of a food typically results in immune tolerance. We also tend to believe there is a critical window in which foods should be introduced. Such introduction encourages the development of tolerance and not allow allergy to take the stage.
Basically, a kiddo is either allergic to a food or immunologically tolerant of a food. Please note: this is specifically describing immune tolerance. This is different from a “food intolerance” like lactose intolerance, which is not related to the immune system.
The Role of Allergy Testing
If a kiddo is either allergic or tolerant of a food, how do we test for these?
Allergy testing includes skin prick testing and blood testing.
Skin prick testing involves applying a small drop of an allergen-containing solution atop the skin. Then, a nurse uses a skin prick device to prick through the drop and into the skin. This exposes those mast cells to the allergen in question. If the mast cells have allergen-specific IgE on their surfaces, then the mast cell “unlocks.” The mast cell releases chemicals, such as histamine, at the site of the skin prick. This release of chemicals causes a red, raised, itchy bump and redness surrounding the bump – a wheal and flare, respectively.
Blood testing involves collecting a blood sample from the kiddo. The laboratory processes the blood, then a machine called ImmunoCAP detects allergen-specific IgE, such as peanut IgE.
Both skin and blood testing determine whether or not the kiddo has allergic antibodies, but neither skin nor blood testing tell us much about the kiddo’s tolerance to the food. So, ultimately, neither skin testing nor blood testing tell us whether or not a kiddo is allergic to a food. What skin and blood testing do is inform an allergist’s clinical decision making.
Testing for Tolerance… and Allergy
Unfortunately, the only test currently available for tolerance is the ingestion challenge. An ingestion challenge is a procedure performed at an allergist’s office. The procedure lasts a few hours and involves the kiddo sequentially ingesting an increasing amount of the food in question. The “goal dose” of the food is typically an average serving size for the kiddo’s age. Allergists use clinical history and prior testing (skin and/or blood) to approximate the risk of the kiddo having a reaction. When a kiddo has a reaction, the ingestion challenge is deemed “positive,” and food allergy is confirmed. When a kiddo does not have a reaction, the ingestion challenge is deemed negative,” and allergy is ruled out. This means tolerance is confirmed.
Thanks for reading this post “Food Allergy: Understanding Allergy Versus Immune Tolerance.” Do you have any questions about food allergies? Reach out to me! And be sure to check out my other blog posts and podcast episodes about all things food allergy. Thanks for reading!
– Dr. Hoyt
P.S. Food allergy testing can be super confusing, so I've created this awesome ebook to clarify the facts from the fiction! Get your copy today!
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A note from Dr. Hoyt
I have talked about a non-profit…
Pam and I volunteer with the non-profit The Teal Schoolhouse. Its primary program is Code Ana. Code Ana equips schools for medical emergencies like anaphylaxis.
Code Ana’s Online Epinephrine Training Program helps support that goal. Through this program, you will educate yourself while you support this important mission!
A medical emergency response plan is important for everyone at any school. Code Ana's program Med-E Ready is a comprehensive approach to school-focused medical preparedness. This program guides schools through the process of creating a medical emergency response plan. A response team is also developed! This is one of the most important components of a school's food allergy policy!
Does your kiddo’s school have Code Ana?
You've just read Dr. Hoyt's post “Food Allergy: Understanding Allergy Versus Immune Tolerance.” Remember, she's an allergist, but she isn't your allergist, so talk with your allergist about what you've just learned!