Maybe We’re Not Allergic to Everything After All

You’re allergic to bananas. You don’t put them in your cereal, you don’t drink smoothies, you don’t travel to Central America. You even hate monkeys, they like bananas so much. Your whole life, you’ve avoided bananas because your mom told you that your doctor did a test when you were a kid and said bananas could kill you. But maybe it’s not so simple. Maybe, just maybe, a banana won’t kill you after all.

A study published in this week’s Journal of the America Medical Assocation highlights the complexity of diagnosing and treating allergies. The paper is a review of more than seventy other research studies, which the authors summarize as “critically limited by the lack of uniformity for the diagnosis of a food allergy, severely limiting conclusions about best practices for management and prevention.” Basically, the authors came to the clear conclusion that, when it comes to diagnosing food allergies, there is no clear conclusion.

Given the confusion over diagnosing food allergies, the authors believe that of people who have possible allergy symptoms and a positive allergy test, more than 50% of them are not actually allergic. In other words, a lot of people who think they’re allergic to bananas actually are not, even when they have the medical tests to back them up.

There are millions of people in the US with true allergies, including banana allergies. Every year, a few hundred die from anaphylactic reactions. Unfortunately, the seriousness of their condition is diluted by fearful patients and parents who unknowingly exaggerate potential allergic reactions to the point that children with food allergies are a laughing matter. Peanut-free zones in schools are ridiculed, concerned parents are caricatured as over-protective yuppies, and allergy sufferers are painted as histrionic whiners. Too many people cry wolf, to the detriment of everyone who truly experiences serious food allergies.

Why are so many people convinced they or their children are allergic to certain foods, when actually they’re not? First, some people are confused about the difference between a food allergy and food intolerance. An allergy is a specific response from the body’s immune system, involving multiple complex biochemical pathways and mediators such as IgE and histamine. Most forms of food intolerance, such as lactose intolerance, are not the same. Many people who think they’re allergic to a food or medication are not allergic, they’re intolerant. Abdominal cramps and gas after drinking a glass of milk are not a sign of allergy, they’re a sign of lactose intolerance. Hives, lip swelling, and shortness of breath after drinking that same glass of milk are signs of true allergy. The distinction is important, because while the prior is uncomfortable, the latter is sometimes life-threatening. Allergies require specific treatment with anti-histamines, steroids, and epinephrine, while food intolerance does not respond to these measures.

“Ah ha,” you say. “I know the difference between allergy and intolerance. I know I’m allergic to bananas, because I got tested, and the results were positive. I’m truly allergic!”

Well, maybe, maybe not. One of the points this study made was that many allergy tests do not accurately diagnose allergies.

Allergy tests can be blood tests or skin test. Blood tests, known as immunoassays, check your blood for the presence of antibodies to specific foods, medicines, insect venoms, or environmental factors such as dust mites. But the presence of the antibody to bananas is no guarantee that you are actually allergic to bananas. While higher levels of antibodies mean you are more likely to be allergic, many people with antibodies against a certain food have no symptoms when they eat it. So a positive test just means you might be allergic, it does not mean you’re definitely allergic to that food. A negative test, on the other hand, means it’s extremely likely you are not allergic to that particular item.

Skin prick testing, or SPT, is an alternative to blood testing to diagnose allergic reactions. After stopping any anti-allergy medicines, your skin is pricked with small needles, each containing a minute amount of a different potential allergen. If you are allergic to the substance, you will develop a hive at the site you were pricked. SPT is risky if you have had a severe allergic reaction called anaphylaxis; a blood test is much safer. Similar to the blood test, a positive result on the skin test does not guarantee you are allergic to that substance. Many people have skin reactions to the test but do not have any allergic reaction when they actually eat the specific food.

So the bottom line is, medical testing over-diagnoses allergies, and many people are needlessly worried about their reaction to a peanut butter and banana sandwich. On the other hand, some do have legitimate concern as true allergies do exist.

What group are you in? If you’ve had a serious allergic reaction to a food, and not just a positive blood test, it’s obvious: you should avoid the trigger and talk to a doctor about whether you need an epi-pen. But if you think you’re allergic only due to results from a blood or skin test, chances are you might be missing out on some tasty meals for no good reason. Talk with an allergy specialist about doing a test called an oral food challenge (OFC).

OFCs expose people to the food which they believe they are allergic to. In a safe medical setting, you will eat gradually increasing amounts of the food over several hours to determine whether you truly are allergic. OFCs are not recommended for people who have previously experienced a life-threatening allergic reaction called anaphylaxis. Given they do carry a small risk of a severe allergic reaction, OFCs are also not recommended for foods that are easily avoidable. In general, less than half of patients have positive reactions in OFCs-implying that most people who think they are allergic to a food actually are not, even if they had a positive blood or skin prick test.

While many people definitely have serious food allergies, a large number-perhaps a majority-of people who think they have allergies actually do not.

Photo Credit: Jason Gulledge

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