Plus, what to do if you experience any sign of a food allergy.

By Cynthia Sass, MPH, RD
April 24, 2019

Maybe you had a reaction to an omelet, or a tuna fish sandwich, and now you're trying to figure out if it was a sign of a food allergy, or just a food intolerance.

A true food allergy—which can develop at any age—is very different from an intolerance. The symptoms of an intolerance can generally be blamed on a missing digestive enzyme; the body isn't able to break down the offending food, which often leads to unpleasant digestive issues (like an upset stomach or bloating).

An allergic reaction, on the other hand, is caused by an immune system response. It typically happens within minutes of consuming the allergen, but can occur up to several hours later.

Food allergy symptoms range from somewhat mild to serious. But, it’s important to note that they can be unpredictable: Symptoms can worsen rapidly. And a food that once triggered a merely uncomfortable reaction can cause a more frightening reaction the next time.

The symptoms of an allergy can even become life-threatening. Such a severe reaction is called anaphylaxis, and involves more than one system in the body. Signs may include swelling of the throat, tongue, and lips; shortness of breath and wheezing; trouble swallowing, or the sensation of a lump in the throat that makes it difficult to breathe; feeling confused or weak; a severe drop in blood pressure; fainting; chest pain; and a weak or abnormal pulse. If you ever experience any of these symptoms, call 911 immediately.

RELATED: What's the Difference Between a Food Allergy and Food Intolerance? 

Other, less severe signs of a food allergy include skin redness, hives, or eczema; sneezing, nasal congestion, or a runny nose; a dry cough; an itchy sensation in the mouth or ears; an odd taste or tingling in the mouth; stomach pain, nausea, vomiting, or diarrhea.

If you are allergic to a particular food, even a very small amount can trigger a reaction. And again, your symptoms can be much worse than they were in the past. So when you have a true allergy, the allergen must be strictly avoided. (This explains why flight crews don't serve peanuts if one passenger is allergic.)

The most common food allergens are milk, eggs, peanuts, tree nuts, soy, wheat, fish, and crustacean shellfish. Known as the Big-8, these foods account for about 90% of all food allergies in the U.S. But it is possible to be allergic to a number of other foods. If you think you may have a food allergy, carefully avoid the suspected food and see an allergist ASAP for testing.

If you test positive, your doctor may prescribe an epinephrine auto-injector (like an EpiPen) that you can carry with you, just in case you ever develop a severe reaction. She can advise you on avoiding accidental ingestion of the allergen, too. 

You may also want to consult with a registered dietitian who can help ensure that you're still meeting your nutrient needs while avoiding the food or foods you're allergic to.  

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Cynthia Sass, MPH, RD, is Health’s contributing nutrition editor, a New York Times best-selling author, and a consultant for the New York Yankees and Brooklyn Nets.

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