Food allergy
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Food allergy
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Content Reviewers
Rishi Desai, MD, MPHContributors
Kaia Chessen, MScBMC
Gil McIntire
Alex Aranda
Evan Debevec-McKenney
A food allergy is a medical condition where there’s an abnormal immune reaction to some food.
Now, a variety of food proteins can cause food allergies, but the most common are known as the big eight, these include proteins within milk, eggs, peanuts, tree nuts, seafood, shellfish, soy, and wheat.
Food is essential to life, and normally food doesn’t cause an allergic reaction - in fact, the process that allows for that is called oral tolerance.
Let’s see how that works. Normally, when food travels through the stomach and intestines, the proteins within them are broken down by gastric acid and proteases into tiny fragments, called oligopeptides - small strings of amino acids.
These oligopeptides reach the Peyer’s patches which are bits of tissue along the intestinal wall where M-cells live.
M-cells are antigen-presenting cells in the gut that grab protein fragments from the intestines and then present them on their cell surface to a nearby helper T cell.
The protein fragments are presented by the M-cell using an MHC class II molecule, which is basically a serving platter for the helper T cells.
The helper T cell is key because it largely controls the immune response.
Now here’s the catch, even if a helper T cell binds to that oligopeptide, another type of T cell called a regulatory T cell can release cytokines so that the helper T cell undergoes anergy.
Anergy is a bit like turning off that helper T cell so that it doesn’t induce an immune response.
In other words, regulatory T cells release cytokines in the lining of the intestines to help prevent the helper T cells from ever getting stimulated by food.
Summary
A food allergy is an immune system response to a food that the body mistakenly believes is harmful. When someone has a food allergy, the body's immune system produces antibodies called IgE (immunoglobulin E) in response to proteins in the food. These antibodies attach themselves to cells that line the respiratory tract, digestive tract, and skin.
When the person eats or inhales the food containing those proteins, the IgE antibodies trigger the release of histamine and other chemicals. These chemicals cause allergic symptoms such as wheezing, chest tightness, nausea, vomiting, cramps, diarrhea, itchy skin or throat, swelling of lips, tongue, and eyes, or anaphylaxis. Food allergies can be life-threatening, so it's essential to be aware of them and take steps to avoid exposure to the offending food.
Sources
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Yen & Jaffe's Reproductive Endocrinology" Saunders W.B. (2018)
- "Bates' Guide to Physical Examination and History Taking" LWW (2016)
- "Robbins Basic Pathology" Elsevier (2017)
- "Food allergy: Epidemiology, pathogenesis, diagnosis, and treatment" Journal of Allergy and Clinical Immunology (2014)
- "Review article: the diagnosis and management of food allergy and food intolerances" Alimentary Pharmacology & Therapeutics (2014)
- "Early introduction of foods to prevent food allergy" Allergy, Asthma & Clinical Immunology (2018)
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