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What's the Difference Between Food Allergy and Food Intolerance?

US News & World Report - Health logo US News & World Report - Health 4 days ago Michael Blaiss, M.D.
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Have you been bombarded with all the news out there related to reactions to food? Terms like food allergy, food sensitivity and food intolerance are batted around as if they're the same thing. But are they? Let's take a look.

A food allergy is an immediate reaction to a food related to a specific antibody to that food called IgE. Almost all the symptoms appear within a few minutes of eating the offending food.

Food allergy reactions can involve many different organ systems. The skin is the organ most commonly involved, with hives and/or swelling.

Some patients can develop difficulty breathing and may also experience wheezing, vomiting, diarrhea, a drop in blood pressure, throat closing off, seizures and even death.

This is anaphylaxis, and it is a true medical emergency. All patients with food allergy must avoid the food(s) causing allergy and carry an autoinjector of epinephrine.

According to the American College of Allergy, Asthma and Immunology, the most common foods that can lead to food allergy are peanuts, tree nuts, milk, wheat, egg, fish, shellfish, soy and sesame.

How do you know it's a food allergy? Usually there's a history of symptoms, and either allergy skin tests or blood tests are performed to document IgE antibodies to the food(s).

There may be times when your history and allergy tests aren't conclusive, and an oral challenge to the food must be performed under the supervision of a board-certified allergist in a facility that is equipped to handle an allergic reaction.

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Food intolerance or sensitivity is a different condition from true food allergy. It can involve many symptoms, usually affecting the gastrointestinal tract.

Unlike a true food allergy, a food intolerance may take hours or even days to develop after eating the offending food.

Symptoms may last hours to days. GI symptoms can vary and may include stomach ache, bloating, nausea and diarrhea.

Other symptoms linked to food intolerance are headaches, joint problems, reflux and fatigue. Unlike food allergy, food intolerance does not progress to a life-threatening reaction.

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Certain foods are more likely than others to cause food intolerance. For example, some people are missing the enzyme lactase that breaks down sugars in dairy products and this leads to problems.

Lactase deficiency can cause gas, abdominal pain, nausea and bloating if the person accidentally consumes dairy.

Gluten is a protein found in certain grains – such as wheat, barley and rye – and is linked to numerous conditions of food intolerance.

Celiac disease is an autoimmune disorder due to antibodies produced when eating gluten. The antibodies damage the small intestines and can lead to diarrhea, bloating, gas, weight loss, skin rashes, fatigue and depression.

Diagnosis of celiac disease can be confirmed by blood tests and biopsy of the small intestine. Treatment involves maintaining a strict gluten-free diet.

In a phenomenon known as non-celiac gluten sensitivity, a patient can have symptoms that suggest celiac disease and feel better after going off gluten products – but all tests for celiac disease are negative.

Currently, no immunologic abnormality has been documented in these patients. Other examples of food intolerance are chemicals in foods.

Caffeine in coffee, tea and soda can cause symptoms in some people, such as irritable bowel syndrome, headaches, nausea, fatigue and anxiety.

Natural chemicals like salicylates, which are found in foods and food additives like tartrazine and benzoic acid, can cause a variety of GI and non-GI symptoms in susceptible people.

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How do you know if you have a food intolerance? The best approach is to remove any foods from your diet that you believe are causing the problem and see if your symptoms resolve.

If they do, you should re-challenge yourself with the food and see if the symptoms re-develop in order to confirm the cause.

What if you're unsure if a specific food is causing you problems? You could try an elimination diet, which removes the most common foods that cause symptoms and see if you feel better.  Ideally, this should be done under the care of your allergist. 

Food allergy and food intolerance are completely different disorders. If you believe you have a true food allergy or a food intolerance, discuss it with your allergist so that you get the proper evaluation.

It's important to remove any foods from your diet that are causing a problem, but it's just as important not to remove a food from your diet unless it is documented to cause you symptoms.

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