For millions of families, eating is not a simple routine, it is a daily risk calculation. Grocery aisles turn into label-reading marathons. School lunches come with extra questions. Restaurant menus require a plan, not just an appetite. And for people living with food allergies, one wrong bite can trigger symptoms that range from hives and vomiting to anaphylaxis, a fast-moving, life-threatening reaction.
About 20 million people in the U.S. have at least one food allergy, including 4 million children and 16 million adults, according to the Asthma and Allergy Foundation of America. But the prevalence is rising, affecting about one in 13 children and one in 10 adults. Additionally, in 2021, 7.6% of Black children had food allergies compared to 5.3% of white children.
The AMA’s What Doctors Wish Patients Knew™ series gives physicians a platform to share what they want patients to understand about today’s health care headlines.
In this installment, two physicians took time to discuss what patients need to know about food allergies. They are:
- Amber Burnette, MD, an allergist and immunologist in Garden Grove, California, at Southern California Permanente Medical Group and assistant area medical director for Kaiser Permanente Orange County.
- Zachary Rubin, MD, a pediatric allergist and immunologist in Oak Brook, Illinois.
Southern California Permanente Medical Group is part of the AMA Health System Member Program, which provides enterprise solutions to equip leadership, physicians and care teams with resources to help drive the future of medicine.
A food allergy is an abnormal immune response
“One very common question that people ask is, ‘What is the difference between an allergy and an intolerance?’ And it has to do with the underlying mechanism,” said Dr. Rubin. “An allergy is an abnormal immune response to a particular food.”
“A food allergy comes from our immune systems and it’s a hyper reaction of your immune system to something it honestly should not care about, like peanuts or if we’re around cats or grass,” said Dr. Burnette. “But when you have allergies, your immune system recognizes those things as being dangerous to you and has an explosive reaction that can lead to common allergy symptoms.”
“What we usually think of is symptoms such as hives, itching, swelling, problems breathing or vomiting. You could also have a drop in blood pressure or a combination of those symptoms,” Dr. Rubin added. “It could be mild or it could be potentially life-threatening called anaphylaxis. And you could have an allergic reaction to even ingesting a tiny amount of that particular food.”
These allergic reactions “usually occur within about two hours of eating. So, in that immediate two-hour window, a lot of times people will react while they’re still in the middle of their meal, like when they’re still at a restaurant, at home or school,” Dr. Burnette said.
Food intolerance is a digestive problem
Compared with a food allergy, “an intolerance is a digestive problem. It’s usually a problem with being able to break down the food in the digestive tract and typically causes problems such as upset stomach, bloating, abdominal pain and diarrhea,” Dr. Rubin said, noting it is “definitely uncomfortable and can be life altering, but it’s not life threatening.”
“People who have an intolerance will get bloated or gassy because they’re digesting improperly,” Dr. Burnette said. “What happens in lactose intolerance, for example, is you’ve lost an enzyme that you have usually had since birth that allows you to properly digest milk and you digest it incorrectly or wrong and you get gas, stomach pains, bloating and things like that.”
There are three types of food allergies
“Not all food allergies act the same way. Understanding the differences can help people recognize symptoms and know what kind of treatment may be needed,” said Dr. Rubin. “Some food allergies cause fast reactions that happen within minutes to about two hours after eating. This type is called IgE-mediated food allergy.
“Symptoms can include hives, swelling, vomiting, wheezing or trouble breathing, and reactions can be life-threatening,” he added. “These are the allergies most people think of when they hear the term “food allergy,” such as peanut, tree nut, or shellfish allergy. Epinephrine is the main treatment for these reactions.”
“Other food allergies cause delayed reactions that mainly affect the digestive system. These are known as non-IgE-mediated food allergies. Symptoms usually begin several hours after eating and can include severe vomiting, diarrhea, or blood or mucus in the stool, especially in infants,” Dr. Rubin said. “One example is cow’s milk protein allergy in babies. Another is food protein-induced enterocolitis syndrome, or FPIES, which can cause repeated, intense vomiting and dehydration. Because these reactions are delayed and do not involve IgE antibodies, epinephrine does not treat them.”
“There are also food allergies that fall somewhere in between, involving both IgE- and non-IgE-related immune responses. A common example is eosinophilic esophagitis, or EoE,” he explained. “In this condition, certain foods trigger chronic inflammation of the esophagus, which can cause trouble with swallowing, vomiting or feeding difficulties. Symptoms are often ongoing rather than sudden.”
“Some food allergies are fast and dangerous, some are delayed and affect the gut, and some cause chronic inflammation,” Dr. Rubin said. “They are all real food allergies, but they behave differently and require different approaches to diagnosis and treatment.”
Food allergy causes are multifactorial
“We don't have a single simple cause for it. It's multifactorial,” said Dr. Rubin. “Genetics do play a role. So, if you have a family member with a food allergy, you are more likely to develop a food allergy.”
“Skin barrier is also a major driver of food allergies. So, children with eczema are at significantly higher risk of developing food allergies,” he said. “The reason why that may be the case is because when your skin barrier is disrupted and food comes into contact with that inflamed skin, it may increase the risk of a process called sensitization where you're producing allergy antibodies called IgE that cause food allergies.”
“The gut microbiome may also play a role. Children who are given antibiotics as babies or antacids as babies, that can change the bacterial environment of the gut, which plays a role in how food proteins are processed and introduced to the immune system,” Dr. Rubin said. “By taking an antibiotic, you may be decreasing the good, healthy bacteria.”
“We also know C-sections are associated with food allergies. It’s probably a similar issue where the gut is not seeded with maternal bacteria as it goes through the birth canal,” he said, noting there have also “been associations with vitamin D deficiency and developing food allergies. But overall, there are a lot of different factors that play into this.”
These are common food allergies
“There are nine foods that cause 90% of food allergies across the world: cow’s milk, egg, soy, wheat, peanuts, tree nuts, sesame seeds, fish and shellfish,” said Dr. Burnette. “When I was going through training in the early 2000s, the big eight is what we called it because there were eight food groups and then sesame was added.”
“Of course, that means that there are other foods people can react to that aren’t as common, but usually those are the ones we see in children,” she said. “And then as they get older, you can start seeing a bit more of shellfish allergies and some of that has to do with what children are exposed to and what they can actually chew and eat as they’re in infancy versus in adulthood.”
“Every day when I'm in clinic, I'm diagnosing at least one person with a food allergy,” Dr. Rubin said. “So there's still quite a few people being diagnosed with it, but there's now evidence to suggest that peanut allergy rates and food allergy rates may be starting to plateau or maybe even going down because of parents starting to adopt the newer recommendations of introducing these allergenic foods earlier within the first year, or ideally 4 to 6 months of life for babies.”
Sesame allergies are being seen more
“I'm recognizing more sesame allergy in general because of the fact that the labeling laws changed recently, so people are able to identify they had this reaction after,” Dr. Rubin said. “Prior to the FASTER [Food Allergy Safety, Treatment, Education and Research] Act of 2021, sesame was not required to be on food labels.”
Prior to that, sesame would simply be listed along with other ingredients as a spice, which can be anything from cinnamon to ginger or black pepper. “You wouldn’t know that it was actually sesame causing the reaction,” he said. “Right now, sesame allergy is listed as the ninth most common food allergen in the United States and those numbers are probably going to be going up.”
A tick bite can lead to a meat allergy
“Recently in New Jersey, someone passed away because of Alpha-gal syndrome,” which is a tick-borne food allergy, said Dr. Rubin. “It's the first case report of that. Now, this is becoming increasingly recognized and hopefully gets more airtime that people understand this because it's a unique type of food allergy.”
“How is it caused? It's caused by a lone star tick. The Latin name for it is Amblyomma americanum. It's mainly found on the East Coast and the Missouri Valley area, but it's starting to go further north as temperatures are rising,” he explained. “This tick has in its saliva a sugar molecule called galactose-α-1,3-galactose, which is known as Alpha-gal. So, we call it alpha-gal syndrome.”
“All mammals, except for certain primates and humans have the sugar molecule, so when we get bit by this tick, we're introduced to a foreign substance that's large enough that the immune system will create IgE antibodies and you become sensitized to that sugar molecule,” Dr. Rubin said. “That means you become sensitive to any mammalian meat products, dairy and certain medications, and it could be potentially life threatening.
“But what's unusual about it is, especially if you consume a hamburger or steak at dinnertime, the reactions don't happen right away and they're inconsistent. They could happen two to six hours later, or it may not even happen at all,” he added. “Prior to understanding this, there were a lot of folks on the East Coast who would wake up in the middle of the night with hives all over their body, or they'd be wheezing and having trouble breathing, and we would call it idiopathic anaphylaxis.”
“We didn't know what the underlying cause was until scientists at places such as the University of Virginia were able to figure this out because of the fact that there was a medication called Cetuximab that had the sugar molecule,” Dr. Rubin said. “And they realized that that was the common denominator that people were reacting to and who had also been bitten by ticks.”
“This is now potentially the 10th most common food allergen in the United States and growing. We estimate that close to a half a million people in the United States have this,” he said. “It's a public health issue, and we need to keep raising awareness.”
“If you live in an area where lone star ticks are prevalent, be aware that this is a risk. Just like if you live someplace where Lyme is prevalent, you need to be aware that it’s a risk,” said Dr. Burnette. To prevent this allergy, follow “typical measures you would take to protect yourself from getting bitten, such as checking your clothing for ticks after being outside.”
More adults are being diagnosed with food allergies
“A lot of adults are developing food allergies,” said Dr. Rubin, noting that “about half of adults who have food allergies are diagnosed as an adult, not as a kid. And that is increasing, but we don’t really understand why.”
“Once we get into adulthood, we begin to see more shellfish allergy,” said Dr. Burnette. “And it is actually one of the allergies that you can develop at any time in your life and often onsets in adulthood, which is not great. I became allergic to shellfish at 28 years old. I had a sense it was coming because my family history.”
Hormone changes can trigger food allergies
“Sometimes we’ll see—which is something I didn’t really learn about in training, but now I see in practice—is that hormonal changes can cause food allergies to develop too,” said Dr. Burnette. “We’ll often see women as they’re going into menopause, for example, starting to develop food sensitivities they didn’t have before.”
“It doesn’t happen as much in pregnancy, but I see women in their late 40s, early 50s suddenly having food allergies or sensitivities,” she said.
Recognize food allergy symptoms and treat promptly
“Usually, the gold standard is avoidance of the known triggers, which we can help determine if they don’t know for sure,” said Dr. Burnette. “Then carrying injectable epinephrine, which is the first line treatment for anaphylaxis. And that’s the avoidance, carrying epinephrine.”
Echoing that, Dr. Rubin said, “And that’s immediate. You have to take epinephrine immediately at the first little sign that you notice.”
Food allergies can go away
“Over time, your immune system can develop a tolerance, so kids who have allergies to milk or egg usually do outgrow those,” said Dr. Burnette. “Milk, egg, wheat and soy are typically outgrown, whereas peanuts, tree nuts and shellfish tend to be more persistent through their lives.”
“Also, being allergic to certain members of a food group may not mean that a person is allergic to all of them,” she said.
“With tree nuts, you may be able to consume some of the tree nuts, but not all of them as an example,” Dr. Rubin said. “So, you need to follow up with an allergist regularly. Usually for most it's either every six or 12 months depending on the food to track so that you know whether or not it's safe to consume.”
Food allergies are a serious chronic disease
“A food allergy is a serious chronic disease, but it’s manageable,” said Dr. Rubin. “The more that you understand how to navigate the world living with food allergies, the more empowered you’ll be to have a normal, healthy life. That’s really important.”
“It’s also important for people who think they have a food allergy to get the right diagnosis because oftentimes it can be over-diagnosed and we want to make sure that people understand what a true food allergy is so that they can make a more informed choice,” he said, adding that “if you live with a food allergy, you’re not alone.”
To learn more, patients can also check out Dr. Rubin’s new book on the topic, which can “help people navigate their health care decisions and have better conversations with their doctors,” he explained. “And it’ll help debunk a lot of the myths related to allergic diseases so that physicians can learn from it.”
