Think you have a food allergy? Here’s what you need to know

On Nutrition

Food sensitivities, intolerances and allergies are hot topics. A few weeks ago, I wrote about why it’s important to not self-diagnose gluten intolerance. Now, I want to turn to food allergies. If you have a true food allergy, you are already hyperaware of what that means. If you think you might have a food allergy, but aren’t sure, here’s why it’s also important to not fall down the self-diagnosis rabbit hole.

If it seems like food allergies are more common, it’s because they are. Food allergies have traditionally been more common in childhood, and while that’s still true, more adults — even older adults — are developing them. In this country, about 3-8% of children and 1-3% of adults have a food allergy. The most common child food allergies are to cow’s milk, eggs, wheat, fish and shellfish, peanuts, walnuts and soybeans. Among adults, fish and seafood, peanuts, tree nuts, fruits and vegetables are the most common culprits.

Here’s an important distinction to know: Food allergies are not the same as food intolerances. While eating the culprit food can make you feel miserable if you are intolerant to it, it can kill you if you are allergic to it and have an anaphylactic reaction. Food allergies cause an immune system reaction with symptoms that vary in type and severity, generally involving the skin, gastrointestinal tract and respiratory tract. Most symptoms happen within two hours of eating the food, but they can also happen several hours later or even after 24-48 hours. For now, the only “treatment” is strict avoidance of the food. This sounds easy, but studies have shown that many people have accidental exposures, often due to cross-contamination in home, restaurant or industrial kitchens. This is why people with food allergies need to keep self-injectable epinephrine on hand in case of anaphylaxis.

Generally, the first step in diagnosing a food allergy is to rule out food intolerances. For example, you may think you have a milk allergy, when really you’re lactose intolerant, which is totally different. Then, to detect if you have a true food allergy, you need a skin or blood test to measure immunoglobulin E (IgE) antibody response to specific foods. What you don’t want is to be tested for immunoglobulin G (IgG) antibodies. The American Academy of Allergy, Asthma & Immunology states this about IgG testing: “It is important to understand that this test has never been scientifically proven to be able to accomplish what it reports to do. The scientific studies that are provided to support the use of this test are often out of date, in non-reputable journals and many have not even used the IgG test in question. The presence of IgG is likely a normal response of the immune system to exposure to food.”

You may have noticed more ads for at-home food allergy testing lately. While these tests have been on the market for a few years, they can seem more appealing now that we’re trying to avoid becoming exposed to coronavirus. Testing at home is certainly convenient, but that doesn’t mean it’s a good idea. Some tests only measure IgG antibodies. Some ask for a hair sample, which is useless because hair doesn’t contain IgE antibodies in hair. Some at-home DNA testing kits claim to identify food allergies, but the research in this area, while interesting, is not robust enough to yield accurate tests for consumers.

For more information, visit the Food Allergy Research & Education website at foodallergy.org.