Experts call them the “big nine”: milk, eggs, nuts, fish, crustaceans, shellfish, wheat, soy, and sesame. These are by far the most common food allergies—and they can arise at any age. At best, food allergies necessitate caution and lifestyle changes; at worst, they can trigger a life-threatening reaction known as anaphylaxis.
Despite some challenges in measuring the pervasiveness of food allergies, data suggests that rates have exploded in the last few decades. The Centers for Disease Control and Prevention reports that food allergies in children rose by 50 percent between 1997 and 2011. From 2005 to 2014, emergency hospital visits for anaphylaxis among children ages five to 17-years old increased by nearly 200 percent.
In the U.S., research published in the Journal of the American Medical Association shows more than 32 million people have at least one food allergy, including about six million American children—or approximately two kids in every classroom. The data has also revealed clues into how genetics and environment may contribute to the soaring numbers of allergies.
Leading experts spoke to us about the latest research on food allergies and the cutting-edge technology we’re using to fight them.
What is a food allergy?
It’s hard to identify the number of people with particular food allergies in part because there are many kinds of food sensitivities with symptoms that mimic an allergic reaction. For example, lactose intolerance can trigger stomach pain like an allergic reaction—but it is technically a digestive system issue, and not a milk allergy.
The best way to be sure a bad reaction to food is indeed an allergy is to get diagnosed by a doctor, says Ruchi S. Gupta, director at the Center for Food Allergy & Asthma Research (CFAAR) at Northwestern University’s School of Medicine. Once you know it is an allergy, she says, then you can develop a plan to treat it.
What makes a food allergy different from other sensitivities is an immune system response. In an allergic reaction, the body mistakenly sees a harmless foreign protein, such as a peanut protein, as dangerous. (Proteins that cause an allergic reaction are called allergens.) The body then produces an antibody called immunoglobulin E (IgE) to fight off the invader.
These antibodies bind to certain immune cells—eosinophils, mast cells, basophils—which when activated, release a chemical called histamine. This can produce an allergic reaction in any of the four major organ systems: the gut, skin, lungs, and heart. Symptoms include itching and rashes, constricted muscles in the lungs, and vomiting and diarrhea.
When more than one of the four systems are involved—for instance when a patient has symptoms in both the gut, like vomiting, and lungs, like difficulty breathing—it’s called anaphylaxis. In this event, the hormone epinephrine, delivered via an EpiPen injection, can be used to relax and open airway muscles for easier breathing.
“The respiratory and cardiac stuff is easily the most scary because that's really where you're talking about potentially life-threatening reactions,” says Dr. Edwin Kim, division chief of University of North Carolina Pediatric Allergy and Immunology and director at the university’s Food Allergy Initiative.
There are no mild or severe food allergies—just mild or severe reactions. Reactions can be somewhat unpredictable: an allergen that caused a mild reaction in the past could cause a more extreme reaction in the future, and vice versa.
Why are food allergies on the rise?
There are two causes for food allergies: genetics and environmental factors. Gupta says genetics alone cannot account for this rapid increase in allergies. What we do know, Kim says, is that kids are more likely to have allergies if both their parents experience immune dysregulation, whether seasonal allergies or eczema.
Meanwhile, two major theories examine the environmental factors leading to food allergies. The hygiene hypothesis posits that a society’s obsession with cleanliness reduces our early exposures to allergens—therefore making our immune systems more likely to overreact to common harmless proteins and trigger an allergic reaction.
In many parts of the world, kids also spend less time near dirt and livestock as in the past—which could explain why some studies have shown that urban areas have more food allergies than rural areas.
“We often talk about those first hundred days or first year of life and how important they are for infants’ bodies to see different things—that goes for playing in the dirt or exposed to different types of foods,” Gupta says. Fearing their infant might have allergies, parents have become overly cautious introducing foods to their babies, she adds.
But the hygiene hypothesis doesn’t completely address why allergies are on the rise. Researchers have found that high exposures to a certain food (like seafood in Asia) is sometimes associated with a higher prevalence of allergies to that food. This is where the dual exposure hypothesis comes in: this theory posits that the chance of developing a food allergy increases if an infant is exposed to traces of an allergen—by breathing it or touching it—before eating it.
Robert A. Wood, chief of the Eudowood Division of Allergy and Immunology in the Johns Hopkins Children's Center, gives the example of a parent rubbing lotion on their baby’s skin. If the parent has even a very small amount of peanut protein on their hands, the theory holds that it could make the child more likely to develop a peanut allergy later.
These two hypotheses are by far the most studied. Others include how changes in the way we cultivate and package food, as well as whether climate change may play a role.
What treatments are available now, and on the horizon?
Research shows that prevention is key. Food Allergy Research and Education, a nonprofit organization, encourages children to eat peanuts as early as possible; research suggests that similar prevention methods are effective for other food allergies as well, Kim says.
Treatments fall under two categories: immunotherapy, which builds tolerance to the allergen through small doses, and biologics, which stops the IgE antibody that causes allergic reactions.
Immunotherapy treatments have been widely studied, and in 2020 the FDA approved the first (and only so far) such treatment. The drug, Palforzia, is an oral immunotherapy in which small, highly controlled doses of peanut protein are administered via pill each day. The goal of the drug is to prevent a severe reaction in the event of an accidental exposure—meaning that people who take the drug still need to avoid peanuts when possible. Efforts to develop treatments that can treat peanut allergies through patches on your skin are also in clinical trials.
There aren’t any FDA-approved treatments for allergies other than peanuts. Some allergists administer makeshift doses of these allergens to patients, Wood says, but the practice comes with risks. Peanut powder obtained at the grocery story, for example, relies on a commercial food labeling system that isn’t always accurate, making it hard to measure the correct dose.
Because it only targets one allergy at a time, immunotherapy doesn’t do much for the 40 percent of kids who have multiple food allergies. But biologics could provide the answer by blocking IgE antibodies. For example, the drug omalizumab binds to the receptors of immune cells before an IgE antibody can get to it, stopping the allergic reaction from taking place.
Wood expects omalizumab, currently sold under the name Xolaire to treat asthma, could be approved to treat food allergies in the coming years. Instead of a daily pill, it’s a shot administered every two weeks, and early research shows patients on the drug can tolerate a large amount of an allergen. Side effects of the drug include joint pain, dizziness, and fatigue.
Though this is an exciting time for the allergy field, “cure is not in the vocabulary,” Wood says. Both immunotherapy and biologic medicines would need to be taken indefinitely—if a patient stopped treatment, their allergy would resume. “We don’t see anything that resembles a cure right now, but obviously that’s the big goal.”