Why There Is So Much Confusion About Who Has Food Allergies

array of food — Many adults don't find out until much later that they are allergic to one food or another. twomeows/Getty Images

A lot of attention has been given to the increasing number of American kids with serious food allergies, now believed to be one in every 13 children (8 percent). School cafeterias have largely banned peanut butter — peanuts are one of the top triggers — and savvy parents know to quiz sleepover guests on allergies to other common foods like milk, eggs or wheat.

Childhood food allergies are a big deal, because a bad reaction could lead to anaphylactic shock, which if untreated by an epinephrine shot, could be fatal. But kids and their parents aren't the only ones who need to be educated about food allergies and how to respond to a severe allergic reaction. According to a new study, adults have it even worse.

More than 10 percent of American adults now have one or more food allergies, according to the largest in-depth survey of the prevalence of food allergies among adults. Of the 40,000 adults surveyed, 10.8 percent were determined to have a legitimate food allergy to things like shellfish, milk and peanuts (the top three allergies), severe enough to cause telltale symptoms of anaphylaxis like hives, swelling, throat tightening and trouble breathing. And nearly half of the allergies developed as adults.

"One in 10 adults with a food allergy is a lot of adults," says Dr. Ruchi Gupta, lead author of the study and director of the Science & Outcomes of Allergy & Asthma Research program at the Northwestern University Feinberg School of Medicine and the Ann & Robert H. Lurie Children's Hospital of Chicago. "This is a significant problem."

What worries Gupta, a pediatrician and researcher who previously focused on childhood food allergies, is not only the surprisingly high prevalence of food allergies among adults, but the fact that only half of the adult food allergies identified by the survey had been diagnosed by a doctor. Even more alarming, less than a quarter of adults with a bona fide food allergy carried an epinephrine pen, the only way to halt a deadly reaction.

Food Allergy or Food Intolerance?

Clearly more Americans need to take food allergies seriously by talking with their doctors about avoiding certain foods and having an emergency response plan in place. But a second surprising finding that came out of Gupta's study is that a separate and nearly equal cohort of American adults believe they have a legitimate food allergy, but actually don't.

When asked if they were allergic to any foods, a full 19 percent of survey respondents said yes. But when prompted to list the symptoms of their most severe reactions, only 10.8 percent met the standards of a "convincing food allergy" like difficulty swallowing, chest tightening or vomiting. The rest of the respondents cited symptoms like diarrhea, belly pain and itching, which are signs of a food intolerance or other conditions, but not a true allergy.

The confusion stems from a general misunderstanding of what is and is not a food allergy. For example, many Americans (31 percent according to a 2015 survey), believe that the only difference between a food allergy and a food intolerance is the severity of the reaction. Or that people with food allergies can eat small amounts of the offending food without triggering a reaction.

This illustration shows the prevalence of food allergies among American adults.
JAMA Network Open

A true food allergy means that consuming any amount of the allergen, even a tiny sip or crumb, will trigger the immediate and overactive immune response known as anaphylaxis. The severity of the reaction depends on the severity of the allergy. People with a food intolerance, on the other hand, can sometimes eat or drink small amounts of the troublesome food without triggering symptoms. And even when the symptoms are at their worst, they are usually confined to the gastrointestinal tract.

Gupta doesn't blame the nearly 9 percent of Americans who falsely believe they have a food allergy. In addition to food intolerances, which can make people feel absolutely lousy, there are a host of other conditions with symptoms that overlap with true food allergies.

A common one is oral allergy syndrome, in which certain fresh fruits, vegetables and nuts trigger an itching sensation in the mouth and throat, and swollen lips. It looks like a food allergy, but the reaction is actually triggered by common pollen allergies and the symptoms go away quickly. But if your throat tightens and your lips blow up like balloons every time you eat a peach, you could be forgiven for thinking you had a food allergy.

In the food allergy survey, Gupta and a panel of allergists were trying to be as conservative as possible when deciding if a certain bundle of symptoms qualified as an allergy, which means their figure of 10.8 percent of adults with food allergies could be low. The only way to know for sure would be to test each and every person who reported a food allergy, either through a skin prick test or the more dramatic "food challenge," in which an individual ingests a potential allergen in a doctor's office to gauge their immune response. But with a sample size of 40,000, that's not practical.

Not Sure If You Have an Allergy? See a Doctor

Gupta thinks that the key takeaway from the food allergy survey is the importance of talking to a doctor to figure out if your specific set of food-related symptoms is a true allergy or something else. "Because some of [these conditions] are treatable and some of them are life-threatening, so it's important to know what you're dealing with," says Gupta.

And if it turns out that you don't have a true food allergy, that's great news! It means you don't have to spend your life anxiously avoiding certain foods.

"I live with this in my own house," says Gupta, whose daughter has a food allergy. "Avoiding foods is so challenging. I don't want people to live in fear if it's something that could be treatable."

For example, oral food syndrome can often be avoided by cooking the offending fruit or vegetable instead of eating it raw. And people with lactose intolerance — rather than a true milk allergy — can enjoy lactose-free dairy products without giving up the pure joy of an ice cream cone on a hot summer day.

So if you've experienced unpleasant reactions to certain foods, don't suffer in silence. Talk to your doctor or make an appointment with an allergist to get tested. Knowledge is power.

Learn more about food allergies in "The Food Allergy Fix: An Integrative and Evidence-Based Approach to Food Allergen Desensitization" by Sakina Shikari Bajowala MD. HowStuffWorks picks related titles based on books we think you'll like. Should you choose to buy one, we'll receive a portion of the sale.