Dear Doctor: It seems like everyone has a food allergy these days. Is it true that kids can outgrow them? Apparently, the test for this is just to eat a little bit of food and see what happens. Can you do this at home -- with an EpiPen at the ready, of course?
Dear Reader: According to the latest research, close to 4 percent of us have either an out-and-out food allergy or what is known as an intolerance, which makes consuming certain foods problematic.
That number comes from a study published last year in the Journal of Allergy and Clinical Immunology. Researchers sifted through the electronic health records of 2.7 million people, looking for allergy-related data. The analysis identified 97,482 people who had at least one food allergy or intolerance.
The study found food allergies to be more prevalent in girls and women, as well as in people of Asian descent. Shellfish was the most common allergen. This was followed, in descending order, by fruits or vegetables, dairy and peanuts. The researchers targeted adverse reactions that ranged from hives and shortness of breath to anaphylaxis, an allergic reaction so severe that it is potentially life-threatening. And while this latest research is indeed compelling, it's important to note that food allergies are often self-reported, which leaves a bit of leeway in the data.
The test you're referring to in your question is often referred to as a "food challenge." Before we go any further, we'd like to emphasize that no, this should not be done at home, EpiPen or not. Due to the potential for severe and life-threatening reactions, a food challenge should always be performed under medical supervision. The point of the test is twofold. You're looking at whether the food in question still causes an allergic reaction. And if so, how much of the food did it take for the reaction to begin?
Those of you who have taken a food challenge know that you start with a tiny amount of the substance in question, just a crumb, really. Then you wait for a period of time, 20 to 30 minutes or so, to see what the immune system thinks. If all is calm, you then try a larger amount and wait again. This continues until, if there has been no sign of an allergic response, you are able to tolerate a full-size portion of the food in question. The full test takes anywhere from four to six hours.
Between 60 and 80 percent of children who have allergies to eggs or milk will outgrow them by the time they hit their mid-teens. For nut allergies, the numbers are lower. About 20 percent of children allergic to peanuts will go on to tolerate them later in life. For tree nuts, that number drops to 14 percent. Very few children who are allergic to shellfish -- maybe 4 percent -- ever outgrow the allergy. And while some adults may find that they grow to tolerate foods to which they had previously been allergic, that turns out to be a lot less likely than in children.
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