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Food Allergies vs. Food Intolerances

Medically reviewed by Chhavi Gandhi, MD, Susan Kerrigan, MD and Marianne Madsen on January 14, 2023

You knew it was a bad idea. Yet you still indulged in that ice cream cone or enjoyed a spicy taco. Now you’re paying the price. You feel terrible. Just like you did the last time and the time before that. Truth is, just about everyone has foods they avoid because of how they make them feel. The question is–will eating certain things give you an upset tummy or put you in a hospital? It’s not always easy to tell the difference between food allergies and food intolerances. Knowing how they differ can be a matter of life or death. Here are some things to know.


Allergic Overreactions


Like well-trained soldiers guarding a vulnerable castle, our immune system keeps us safe. Every day we encounter things that can make us sick, like bacteria, viruses, and fungi. The immune system’s main conduit is the lymphatic system, where tiny bean-shaped cells called lymph nodes rely on white blood cells to imprison everything from bacteria to cancer. Most of the time, this battle is waged without us even noticing. Sometimes, like warriors setting a part of the castle ablaze to defend it, we notice our immune system when we experience symptoms. When we get a cold, that runny nose or cough is actually a sign that our immune system is hard at work.


However, sometimes our immune system goes haywire. The guards accidentally fire on a visiting dignitary. An otherwise harmless bit of pollen or pet dander brings tears to our eyes or makes us wheeze. Most of the time, these allergic reactions are transitory. Yet with some food allergies, the reaction can be fatal. When you eat, or, in some cases, just touch, a food you are allergic to, your immune system singles out a protein in it as a threat. Allergic antibodies called immunoglobulin E (IgE) cause an immediate reaction. These include hives or itchy skin along with swelling. 


In some rare food allergies, the IgE antibodies are not activated. These reactions are often called food hypersensitivities. The most common type of these non-IgE-mediated food hypersensitivities include food protein-induced enterocolitis (FPIES), allergic proctocolitis (AP), and food-protein-induced enteropathy (FPE). In these conditions, other parts of the immune system are triggered, and the reaction is not immediate. The main symptoms are digestive––like an upset stomach or throwing up. These symptoms can often be confused for food intolerances or sensitivities but because the immune system is in play, it is an allergy. While it is not pleasant, it is also not life threatening.


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Allergic Rhinitis & Conjunctivitis - Risk Factors

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However, severe allergic reactions to foods like milk, egg, wheat, soy,  peanuts, tree nuts/seeds, shellfish and seafood can cause life threatening reactions called anaphylaxis. These symptoms can be mild, from itchy skin and hives, to more severe symptoms causing shortness of breath and a dangerous drop in blood pressure that can be fatal. In the United States alone, up to five percent of the population is estimated to have suffered anaphylaxis––although it can also occur after other triggers such as insect stings and medication reactions. People who have been diagnosed with a severe food allergy often carry epinephrine injectors, but if you or a loved one without a diagnosed allergy experiences these symptoms, seek emergency medical treatment.


Being Intolerant


Perhaps the best known type of food reaction is lactose intolerance. Alone among mammals, humans drink milk (from another mammal, most often cows) long after they are weaned. For most it’s a calcium-rich beverage that improves the taste of cereal and coffee while boosting your day’s protein and Vitamin D. For a few however, the sugar in lactose promotes a stomach-clenching result with symptoms including gas, bloating, nausea, and diarrhea. From childhood on, around 65% of the population has a reduced tolerance for lactose––especially among people of West African, Arab, Jewish, Greek, and Italian descent.


When comparing food allergies versus food intolerances, the difference is that while allergies are an overreaction of the immune system, intolerances most often involve the digestive system. Besides lactose, wheat and other grains that contain gluten are a common source of food intolerance, as is additive sensitivity (like the sulfites in wine and canned goods). Although people with celiac disease, which is caused by an autoimmune reaction to gluten, can suffer from headaches and joint pain along with digestive issues, it is not considered an allergy because they are not at risk for anaphylaxis from ingesting gluten.


If you have found certain foods are a trigger, a medical professional can help differentiate what is an allergy and what is an intolerance. There may be treatment options and even ways to eat more of the things you enjoy without the nasty results. 


Written by John Bankston

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