The allergy-intolerance conflation
Many food allergies are actually food intolerances, Stadtmauer said. “People commonly think an adverse reaction to something is a food allergy. That’s a leap that they should probably not be making.”
According to the National Institute of Allergy and Infectious Diseases, a food allergy occurs after proteins in the food enter the bloodstream and an allergic person’s immune system produces IgE, or immunoglobulin E, an antibody reacting to a certain food. The food-specific IgE then attaches itself to cells in the blood and body tissue, like the skin or nose, setting off allergic reactions such as eczema, coughing, hives or swelling in the mouth.
People with a family history of allergies, including asthma and hay fever, are more likely to have immune systems that form IgE against a food. A person with two allergy-prone parents is more likely to have food allergies than a person with only one. The Institute also states that children often outgrow their food allergies, but many adults have them for life. In what can only be perceived as a cruel irony, people are often allergic to the foods they eat most often.
“A lot of people have an unpleasant symptom that they associate with eating a food and they determine it’s a food allergy,” said Riedl. “There’s a lot of misinformation.”
Food intolerances are more common than food allergies, and are not caused by the immune system. But symptoms of intolerances, like abdominal cramps, may be similar to those of allergies, accounting for the conflation. Intolerances can be caused by factors such as food poisoning, additives like sulfites or MSG, and high histamine levels in some wines, fish and cheeses. In the case of lactose intolerance, an enzyme deficiency is the culprit for a difficulty in digesting lactose.
The distinction between food allergies and food intolerances is important, Riedl said. “The term ‘allergy’ is used colloquially as anything bad that happens when you eat a food. It’s a loose term that’s different from the true definition of an immune-mediated, serious, life-threatening allergy.”
A recent survey published in the Journal of Allergy and Clinical Immunology revealed that the rate of peanut allergies in children has tripled over the past decade. 2.1 percent of children were allergic to peanuts or tree nuts in 2008, compared to just 0.6 percent in 1997.
Is this increase due to misdiagnosis, as the new report claims, or other factors, like food production? Environmental changes like global warming have also been linked to increased rates in allergies like hay fever, according to a study presented in March at the annual meeting of the American Academy of Allergy, Asthma & Immunology.
“Nobody knows why the true prevalence of food allergies, as well as hay fever, asthma, and mediation allergies is rising,” Riedl said. Leading theories for rising allergy rates include the “hygiene hypothesis,” first proposed two decades ago by British researcher David Strachan. The hypothesis suggests that a lack of exposure to germs and bacteria during the formative years have weakened contemporary immune systems, Riedl said, and could result in higher rates of food allergies.
Or perhaps the high prevalence is caused by increased awareness. As Stadtmauer said, “There’s a lot more attention being paid to food allergies, and that also accounts for it.”
Other possibilities include dietary changes, activity levels and even obesity, according to Riedl. “It’s probably related to environmental factors that have changed over the past 100 years,” he said. “But it’s complex. We don’t have a straightforward answer.”