A new study in The Journal of Allergy and Clinical Immunology reports that the rate of peanut allergies in kids more than tripled in just ten years.
According to the study, 1.4 percent of kids reported peanut allergies in 2008, as opposed to just 0.4 percent in 1997. The rate of combined peanut and tree nut allergies reported in kids was 2.1 percent in 2008, compared to 0.6 percent in 1997.
Alarming, but before we panic, let’s take a closer look at the study design: This study randomly surveyed more than 5,000 homes in the US by phone, and the allergies were self-reported.
Is self-reporting an accurate way to assess the prevalence of food allergies?
On the one hand, who knows kids’ food reactions better than their parents, right? But when it comes to food allergies, it seems that even medical experts can’t really agree on what makes a diagnosis of food allergy, so parents’ testimony of their kids’ food allergy status (as opposed to asking them a simple factual question, such as “Did your child get a tetanus shot?”) may very well reflect parental heightened awareness of this medical issue (which is definitely on the rise), rather than a true increase in food allergies themselves.
We know less than we think about food allergies
A recent systematic review in the Journal of the American Medical Association shows the complexity and confusion in the field of food allergies. The researchers, led by Dr. Jennifer J. Schneider Chafen, pored over more than 12,000 studies on food allergies—most of which, they found, were poorly conducted. Only 72 studies met the authors’ criteria for scientific rigor, and when analyzing the data the conclusion was, in plain words, that we know much less than we think.
Here are a few surprising issues the researchers uncovered:
• There’s no agreement on the definition of food allergy.
The lack of clear definition leads to much confusion between what is a food allergy (in which the immune system is involved) and other reactions that are not immune-mediated, such as food intolerance.
• There’s no agreement on how to test for a food allergy, and many tests aren’t definitive. The common tests used to aid in the diagnosis of food allergies aren’t very good at predicting who will actually react to a certain food; test results in isolation (without a good clinical picture and evaluation) aren’t more helpful than a coin toss.
The current gold standard for diagnosing food allergies is the food challenge, during which a physician gives the patient a sample of the suspected allergenic food, and monitors for an allergic reaction. This kind of testing is expensive and requires specialized personnel and therefore isn’t often done (it also isn’t covered by many insurance plans). More commonly used tests are the skin-prick test, during which a dilute extract of the potential allergen is placed under the skin, and a blood test determines the presence of food-specific allergic antibodies known as IgE.
Unfortunately, neither of these two tests is very specific; in fact they aren’t definitive at all. Kids with non-specific symptoms, such as a rash or digestive complaints, and a positive skin-prick or blood test actually have less than a 50 percent chance of indeed having a food allergy.
If definition and testing aren’t clear-cut, it becomes quite evident that the prevalence of food allergies is hard to assess.
The researchers found that in general, studies that used self-reporting found much higher rates of food allergies than studies that used the skin-prick test, IgE blood test and food challenges. The authors comment that it’s even hard to say for sure whether food allergies are in fact on the rise because the data is so inconsistent.
Their best estimate is that the prevalence of food allergies is anywhere between 1 or 2 percent and 10 percent, which is a difference of 500 percent or more. So much for accuracy.
It is generally the feeling in the medical community that food allergies are indeed on the rise, but there’s no doubt that misdiagnosed food allergies are on the rise, too.
And if food allergies are misdiagnosed?
Inappropriate diagnosis of food allergies denies kids nutritious foods and creates unnecessary anxiety around food. Misdiagnosed food allergies also are a waste of money, as specialized diets don’t come cheap.
Over-diagnosis and misdiagnosis of food allergies also may trivialize the seriousness of real, potentially life-threatening food allergies. We all know the story of the boy who cried wolf.
Hopefully, some good news ahead
The way ahead is promising. The National Institute of Allergy and Infectious Diseases is creating comprehensive clinical guidelines for the diagnosis and management of food allergies. Guidelines from a 25-member expert panel are due this fall and will provide much needed direction.
In the meantime let me offer some prudent advice: If you think your child may have a food allergy, it’s best to consult an experienced physician. Over-diagnosis may lead to unnecessary food limitations and undue reduced quality of life, but not taking real food allergies seriously enough and not learning what to do about them can threaten life itself.
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