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The trend is not an entirely American phenomenon. European nations have posted increases similar to the one in the U.S., and in a study of the relatively confined residents of Britain's Isle of Wight, rates of peanut allergies among toddlers doubled from 1989 to 1994. While prevalence in Asian countries, where peanuts are a popular dietary add-in, remains low, experts warn that could simply be the result of spottier awareness, diagnosis and reporting of allergic reactions in those nations. (Read "Allergies Nothing to Sneeze At.")
What's behind the rise in food allergies? Has a generation of kids, or their moms, been exposed to things in the environment or in their diets that could make them more sensitive to certain food proteins? Perhaps. Allergies are the direct result of too much IgE, an immune-system component that serves as the body's supersonar for detecting any foreign and potentially harmful proteins. To signal the need to annihilate these invaders, IgE attaches like antennae to the surface of cells that release histamines and other inflammatory agents. In mild cases, the result is a rash and hives. In others, blood pressure drops and fluid builds up in tissues, leading to swelling. Airways can constrict, triggering coughing and eventually respiratory distress and even death. Once a massive IgE cascade is activated, only a shot of the hormone epinephrine, a.k.a. adrenaline, can stop a hypersensitive immune system from killing the body it set out to protect.
So why are children making so much IgE these days? Part of the fault may lie in modern medical practices: with antibiotics and immunizations to protect against micro-organisms and parasites, children's immune systems may be getting weaker and even bored, with little or nothing to fight. This theory was first posited 20 years ago by a British epidemiologist who noticed that children with more siblings had less hay fever than kids in smaller (and presumably less snot- and germ-laden) families. It could explain the climbing incidence of all allergies — not just those to foods — as well as asthma. Sanitation can't demystify the entire trend, but the so-called hygiene hypothesis remains the leading answer to baffled parents' questions.
For families like the Fradins, however, knowing the why of food allergies is less important than knowing whether their children will be affected — and how. (Noah has a brother who has no food allergies.) Because allergic reactions to food can vary, even within the same person, allergists often shrug when it comes to advising parents about forecasting anything about their child's next reaction. "We really have no test that can tell us who is apt to have a severe, life-threatening reaction and who is more like the vast majority who will never have that kind of reaction," says Dr. Hugh Sampson, director of the Jaffe Food Allergy Institute at the Mount Sinai School of Medicine in New York City.
Even the act of diagnosing allergies has become a source of confusion. Increasing reliance in recent years on a blood-based test instead of the classic skin-prick screening means that not just allergists but also pediatricians can find out if children are carrying IgE antibodies for certain foods. But some positive tests may be false alarms that lead families to spend a lot of energy avoiding common foods that their kids can actually tolerate.