“The statistic is even higher than we see in kids,” Dr. Ruchi Gupta, lead author and professor of pediatrics at Lurie Children’s Hospital and Northwestern University, told Allergic Living.
In 2018, another study from her team estimated that nearly 8 percent of American children have food allergies. Considered together, this pair of pivotal studies reveals a far higher prevalence of food allergies across all age groups than previously appreciated, according to Gupta.
“We are now able to estimate that 32 million Americans have food allergies,” she said. “When you compare that to the previous estimate of 15 million, the significance of this emerging disease becomes obvious.”
To arrive at the adult findings, published in JAMA Network Open, Gupta and her team surveyed 40,443 adults via phone and Internet. Although based on self-reporting, strict criteria were used to include only those whose symptoms were consistent with “convincing” food allergy.
Allergic Living breaks down the important takeaways of the study. (We also address how the media’s coverage of the findings missed the mark in a separate article here.)
1. Food Allergies Abundant Among Adults
In this large study, the number of American adults with food allergies has about doubled compared to previous research. In 2014, a study from New York’s Icahn
“Food allergies are clearly a significant issue in adults,” says Gupta. “We saw 1 in 10 adults have convincing signs of a food allergy, so it is really important to examine this further.” She notes as well that “almost half of these adults reported developing at least one allergy as an adult.” Plus, half of the “convincing” group had multiple food allergies.
To be considered someone with a convincing food allergy, a survey participant’s most severe reported reaction had to include at least one symptom from the research team’s “stringent symptom list,” which included trouble breathing and vomiting.
Gupta says the “why” of the prevalence is less clear than its existence. “This study just opens up a hundred more questions,” she says. Those include public health implications if so many adults face the risk of potentially severe reactions – and since, as this and other studies suggest, they are often not carrying epinephrine for prompt treatment.
An intriguing societal factor is that the surge in childhood food allergies was first noticed in studies using data from the 1990s and early 2000s. Those “kids” are now young adults. “With so many adults not outgrowing their childhood allergies and more developing new allergies as an adult, we need to focus our research on adults and potential factors contributing to this increase in adult onset food allergies,” Gupta said.
2. Adult Onset Allergies on the Rise
A big concern the lead author has is the rate at which food allergies appear to be developing in adulthood. Of the 26 million adults with allergies the study revealed, at least 12 million (48 percent) developed a food allergy after the age of 18.
“What type of environmental triggers lead to adults developing allergies to foods they could previously eat?” she asks. “We have the numbers, but now we need to understand what they mean.”
“We would particularly urge them to consult their physician about any suspected allergies to ensure that they are prepared to manage their allergy day-to-day,” Warren says.
“The reported new onset food allergy is a very striking take-home message from this work,” says Dr. Brian Vickery, allergist and director of the Food Allergy Center at Children’s Healthcare of Atlanta. He notes that some people lose tolerance to foods, such as those who eat shellfish their whole lives and then suddenly in their 40s have a severe reaction.
Vickery is fascinated by emerging research on alpha-gal or red meat allergy, in which the environmental factor of a tick bite is increasingly making adults allergic to food they’d previously eaten without issue.
“What if that is just the tip of the iceberg?” he asks, acknowledging that so far this is just speculation. “There could be a lot of other things we are exposed to that we currently don’t recognize that shift people’s immunity throughout life.”
3. Those Who Misread Symptoms as Food Allergy
The Northwestern researchers found that a much larger percentage – 19 percent of American adults – think they have a food allergy. Of this overall group, over 10 percent had a convincing allergy, while slightly less than 9 percent had symptoms that were not consistent with an immune system-mediated food allergy.
“There are a lot of food-related conditions and a lot of times the symptoms overlap,” Gupta points out. “That’s why it’s so important to figure out what it is.”
The researchers say the level of incorrect self-diagnosis shows how important it is for patients to visit an allergist for proper assessment. Since a food allergy requires the strict avoidance of a food or foods, “I don’t want people eliminating foods from their diet unnecessarily,” Gupta stresses.
4. Epinephrine Use, Hospital Visits
Many adults with a history of severe allergic reaction may not be fully prepared to manage an anaphylactic event. In the Northwestern study, only 24 percent of the “convincing” allergy group reported owning an epinephrine auto-injector, while 38 percent of adults said they had visited an emergency department for treatment of a food allergy reaction.
“Among adults with a likely food allergy, we remain concerned with the relatively low rates of current epinephrine prescriptions,” says Warren.
5. Most Common Adult Food Allergies
According to the researchers, the most common food allergens today among adults are:
Shellfish – 2.9% or 7.2 million adults
Milk – 1.9% or 5.7 million
Peanut – 1.8% or 4.5 million
Tree nut – 1.2% or 3 million
Fin Fish – 0.9% or 2.2 million
Peanut allergy was physician-diagnosed among 72.5 percent of adult patients. Of concern, despite the convincing evidence that patients had shellfish allergy, only 42 percent of respondents saw a doctor to confirm the diagnosis.
As far as milk being the second-most common allergy, Warren says the team found that “surprising,” but more research is needed to understand why that level has increased from previous adult studies.