Allergy, Sensitivity, or Intolerance? A Guide to Food-Reactivity Issues

Seven years ago, at age 28, Taj Ruler was diagnosed with ulcerative colitis, a harsh form of inflammatory bowel disease (IBD). The Minneapolis-based performing artist had suffered from chronic stomach pain and frequent, urgent trips to the bathroom for some time before a colonoscopy led to her diagnosis.

Given that many of her symptoms matched those caused by food sensitivities, she worked with a nutritionist to test for them. The results panel, with its color-coded system of green, yellow, and red to indicate severity, revealed that her body was responding poorly to multiple foods.

“The only one that was red was chocolate — that was a real bummer!” Ruler recalls.

But a host of other foods also seemed to be causing uncomfortable gastrointestinal (GI) symptoms for her. So, with the help of her nutritionist, Ruler embarked on a strict elimination diet.

For the first week, she was limited to peaches, bananas, avocados, and sweet potatoes — some of the only foods that didn’t show a reaction on her food panel. “That really sucked,” she says. “I made a lot of smoothies.”

Her symptoms began to stabilize through an approach that combined diet, medication, and support for mental health, and she was gradually able to reintroduce more foods. Today, she follows what she calls “a kind of expanded paleo diet,” which includes staples she once feared she’d never be able to eat again, such as rice and potatoes.

“Now it’s all about experimenting with what foods feel good and which are still challenging for my body to process,” she explains. “I’m learning there’s a lot that I can have in moderation.”

Time and patience were key for Ruler to feel ready to start expanding her diet. “For a while, food was scary because of how it could make my body feel. It took a lot of trying things in small doses. Now I’m able to have things I couldn’t have for years because I was too scared. One day, I’m really hoping to add chocolate back in.”

She is far from alone in navigating the challenging world of food reactivity. Food allergies, intolerances, and sensitivities are all on the rise. Our experts answer common questions about food reactivity and offer ideas for how to cope.

What is a food allergy?

“‘Food allergy’ has become a blanket term for a negative reaction to food,” says Northwestern University pediatrics and medicine professor Ruchi Gupta, MD, MPH, author of Food Without Fear: Identify, Prevent, and Treat Food Allergies, Intolerances, and Sensitivities. But the term is often used incorrectly.

Precisely defined, a food allergy is a medical condition in which exposure to a food triggers an immediate, marked immune response. These typically involve immunoglobulin E (IgE) antibodies but occasionally involve different parts of the immune system.

Precisely defined, a food allergy is a medical condition in which exposure to a food triggers an immediate, marked immune response.

“Antibodies are like guided missiles that the immune system produces against things like viruses but also against foods,” explains naturopath Dan Lukaczer, ND, director of medical education at the Institute for Functional Medicine. While food sensitivities can also involve the immune system (more on that later), allergies are usually distinguished by the involvement of IgE antibodies. These antibodies can be identified with blood tests.

The symptoms can range from mild (an itchy or tingling mouth, a few hives) to severe (tongue swelling, difficulty breathing). In some people, a food allergy can trigger anaphylaxis — tightening in the airways, a severe drop in blood pressure, and loss of consciousness.

“With food allergies [involving IgE antibodies], the reaction is immediate and sometimes dramatic, often occurring within seconds to minutes,” Lukaczer says. And it doesn’t take much of the offending food to cause a response. “Small amounts, such as one strawberry or a small amount of dairy, can cause reactions.”

What is a food sensitivity?

Food sensitivities are a tricky category, and definitions vary. One theory suggests that, like allergies, they may involve an immune response, though they activate a different antibody, immunoglobulin G (IgG). “Food sensitivity is an immunologic reaction in the same way that allergy is, but it’s delayed, with reactions usually occurring after hours or days,” says naturopathic doctor Sara Jean Barrett, ND, a holistic and functional-medicine practitioner in Minneapolis.

Gluten, corn, dairy, soy, and eggs are some of the best-known triggers for food sensitivities. Reactions can include joint pain, stomach pain, fatigue, rashes, and brain fog.

“Food sensitivity is an immunologic reaction in the same way that allergy is, but it’s delayed, with reactions usually occurring after hours or days.”

Because symptoms of food sensitivity often occur hours or days after a food is consumed, identifying triggers can be more of a challenge. “If you eat something on Monday and have a migraine on Wednesday, it can be harder to connect the cause and effect,” says Lukaczer.

Many tests claim to identify sensitivities by testing for IgG antibodies. But unlike allergy tests, IgG tests aren’t standardized, and many providers believe they should be used with caution. False positives are common, and a test may indicate that someone is creating IgG antibodies against a food that isn’t causing any negative reactions.

“If you’re eating something and have no symptoms, don’t take it out of your diet just because a test shows something,” Gupta says.

Others feel differently. Lukaczer believes that IgG tests can be valuable if used judiciously. “You have to use tests with a degree of balance in the context of each patient.” If someone is experiencing symptoms, a food-sensitivity test can help inform treatment.

“The gold standard of testing is eliminating a food and seeing if there’s improvement. An IgG food-sensitivity test gives me a road map to see which ones we may want to assess,” he says. “It can help narrow the field.”

What is a food intolerance?

Some symptoms of food intolerance (such as stomach pain and nausea) can overlap with those of allergy, but an intolerance does not involve the immune system. It usually occurs when a person’s body doesn’t produce an enzyme needed to digest a certain food. For instance, lactose intolerance is the result of the body not making enough lactase, the enzyme that digests milk sugars.

Symptoms of an intolerance — bloating, cramps, diarrhea — generally involve the GI tract, but they can also extend to headaches and mental fogginess, says Gupta. “These symptoms are uncomfortable but not life threatening.”

Symptoms of a food intolerance are uncomfortable but not life threatening.

Common food intolerances include lactose, caffeine, and eggs.

Some of these can be acquired with age, says Barrett. Nutrient deficiencies can reduce our ability to make digestive enzymes, as can illness, infection, and medications that affect the gut.

Intolerances can also be tricky to pin down, Barrett notes, because you can’t test for them in the blood. They can only be identified by eliminating the suspected food and seeing if symptoms improve.

What are common triggers for food intolerances and sensitivities?

Food intolerances and sensitivities are typically preceded by the development of a leaky gut. The list of factors that can contribute to the condition is a long one: acid blockers, nonsteroidal anti-inflammatory drugs (NSAIDs), stress, parasites, unfriendly bacteria, alcohol, a low-fiber diet, zinc insufficiency, additives in processed foods, common chemicals and pesticides, and more.

When any of these factors stress the GI system, gaps may form between the junctures of the gut lining. This allows food proteins to escape into the bloodstream, where the immune system sees them as invaders to be vanquished.

“To make an IgG reaction, a string of amino acids from a food slips into the bloodstream and triggers an immune response. There needs to be gut permeability for that to happen,” Barrett explains.

(For more on leaky gut syndrome, see “How to Heal a Leaky Gut“.)

Is food reactivity on the rise?

According to a study published in 2019 that included 40,443 participants, about 10.8 percent of Americans have an allergy to one or more foods. People can be allergic to any food, but the nine most common culprits are peanuts, milk, shellfish, tree nuts, eggs, finfish, wheat, soy, and sesame.

About twice as many — one in five — American adults believe they’re allergic to a food, says Gupta. “But half of those folks may be suffering from another food-related condition, such as an intolerance.”

In the 2019 study referenced above, Gupta and her coauthors found that nearly half of the participants reporting food allergies had developed at least one of them as an adult.

“Food allergies are not just a childhood thing anymore,” she notes. Shellfish are the most common adult-onset allergen, but allergists are seeing increasing reactions to the other top-nine foods.

10.8% of Americans have an allergy to one or more foods.

Food allergies are also on the rise in kids. Allergic reactions in children increased by 50 percent between 1997 and 2011, according to the Centers for Disease Control and Prevention. Between 1997 and 2008, the prevalence of a peanut or tree-nut allergy in U.S. children more than tripled. In Gupta’s research, one in five parents reported having taken their child to the ER in the past year for a food-related allergic reaction.

There’s no single trigger for this dramatic rise in food allergies, although there are several likely culprits. A 2018 study of 792,130 infants, published in JAMA Pediatrics, found that babies who were given acid-suppressive medications or antibiotics in the first six months of life had an increased risk of developing nearly every kind of allergy, including food allergies. “Not having the right [gut] bacteria in the right quantities is one of the top hypotheses for the rise in food allergies,” says Gupta.

Other contributing factors may include overly sanitized environments and the low-fiber standard American diet, which weakens the gut microbiome.

Widespread use of antibiotics and NSAIDs and exposure to chemical pesticides and environmental toxins have been implicated in damaging the gut lining and triggering leaky gut. This can lead to allergies, intolerances, and sensitivities to food. (For more on repairing a leaky gut, see “The Little Molecule That Could” on page 38 of the May 2022 issue of Experience Life.)

What chronic conditions might be exacerbated by food reactivity?

“Irritable bowel syndrome (IBS) is high on the list,” says Lukaczer. IBS symptoms can include constipation, diarrhea, gas, and bloating.

Crohn’s disease, ulcerative colitis, and other inflammatory bowel diseases (IBD) are also not directly caused by food reactivity. These are immune-mediated autoinflammatory conditions with a genetic component. But, as in Ruler’s case, food sensitivities can make symptoms worse. And children diagnosed with IBD also tend to struggle with IgE-mediated food allergies.

Autoimmune conditions share some common underlying factors with food allergies and reactions, particularly leaky gut. “When I see someone with an autoimmune disease, I think of increased intestinal permeability,” says Lukaczer. Eliminating foods that may be causing an immune response can mitigate symptoms while allowing the gut to heal.

Do environmental toxins play a role in food reactivity?

In 2021 a group of Yale immunobiologists published a paper in the journal Cell arguing that substances in processed food, as well as chemicals in common household items such as dishwashing detergent, might be disrupting our normal immune response to food. When the immune system encounters noxious substances along with food, they note, this can cause “the immune system to react to food proteins the way it would react to toxic substances.”

Glyphosate — an ingredient in the herbicide Roundup, which is commonly sprayed on corn, soybeans, wheat, and oats — has also been shown to damage the gut lining and disturb the microbiome. Some research suggests that widespread use of glyphosate might be linked to the rise of celiac disease, an autoimmune condition in which dietary gluten damages the small intestine.

Mercury in fish can also contribute to gut permeability, says Lukaczer.

Can food reactivity be healed?

Various strategies have been employed to curb intolerances, sensitivities, and even many allergies.

Providing the digestive enzyme the body is missing can help ease intolerances, says Barrett. Two over-the-counter options are Lactaid, which offers the lactase enzyme to break down lactose in dairy products; and Beano (alpha-galactosidase), an enzyme that digests galactose, a simple sugar found in beans, broccoli, cruciferous vegetables, and some grains.

“Sometimes we can figure out why someone isn’t making an enzyme and work on that too,” she adds.

Many sensitivities can be healed over time.

Many sensitivities can be healed over time. “If you can avoid the food long enough and do enough gut healing, you can slowly reintroduce the food and not have the same immune reaction,” Barrett explains.

Healing a leaky gut can have a profound effect on improving symptoms such as migraines or IBS. “Then over time, people can often reintroduce foods in moderation or in rotation,” says Lukaczer.

Not all food allergies can be resolved — and when anaphylaxis is a potential, it often feels too risky to experiment. But Gupta notes that we now have the first FDA-approved oral immunotherapy (OIT) for peanut allergies in children. OIT trials for other foods are showing promise, and clinical trials are under way for epicutaneous and sublingual immunotherapy options for food allergies.

Additionally, researchers are studying biologics as combination and standalone therapy. (Make sure to discuss treatment options with your allergist.)

That’s hopeful news for people struggling with life-threatening allergies, for whom the worry of accidentally eating the problem food is ever-present.

Does food reactivity increase the risk of disordered eating?

It can, because it often necessarily identifies otherwise wholesome foods as harmful. “We have to be careful to talk about food in a way that doesn’t create orthorexia,” says Barrett. Orthorexia is an eating disorder in which someone is fixated on eating only “good” or “healthy” foods. “We want to focus instead on what makes your body feel good, rather than saying, ‘This is a bad food.’”

Lukaczer sometimes sees patients who believe they’re reactive to many foods after seeing their score on a food-sensitivity test. “But they’re still not doing well after eliminating those foods, so there’s something else going on.” He focuses on helping them improve their digestion and gut health while decreasing their exposure to toxins and improving their nutrition, with an eye toward aiding them as they expand their diet as much as possible.

As in Ruler’s case, sometimes people who have experienced negative reactions to certain foods can be understandably fearful about reincorporating them. Working with a functional nutritionist or doctor can be helpful in these cases.

Why is it important to reintroduce foods over time, when possible?

Different foods deliver a range of nutrients and fiber, so maintaining a broad diet helps nurture a diverse gut microbiome. And restrictions can be stressful, so having fewer of them can be easier on the mind.

“For both mental and physical health, it’s really important to eat the widest variety of foods possible,” Barrett says. When she identifies several foods that may be contributing to a patient’s symptoms, she advises reintroducing the foods one at a time after an elimination period to see if they cause a reaction. If a food does cause a reaction, she asks the patient to try it again in another few months. “With an allergy you wouldn’t do that, but a sensitivity may be overcome, so we want to try to reintroduce those foods.”

It’s also important to pay attention to your body so you can identify what really doesn’t work. “Not everyone can eat everything again,” says Lukaczer. “Sometimes a person just doesn’t do well with corn or dairy or gluten — but that doesn’t mean they should stay away from all of them.”

If you find yourself shying away from a food group solely because you’re afraid it will cause trouble, try adding those foods in, even in small amounts. Doing so will support microbial diversity in your gut — and probably make eating more pleasurable.

What are the best strategies for coping with and recovering from food reactivity?

If symptoms are severe and complicated by other diagnoses, such as an autoimmune condition, Barrett recommends working with a functional-medicine practitioner or nutritionist for support. Those dealing with mild symptoms might opt to start with some DIY experimentation in the form of a simple elimination diet, such as Whole30, or the elimination diet protocol developed by the Institute for Functional Medicine. (For details on this protocol, see “The Institute for Functional Medicine’s Elimination Diet Comprehensive Guide and Food Plan“.)

“If you do that for a few weeks and feel better, don’t just stop. Take the time to do the reintroduction portion,” advises Barrett. Try each food for a few days before reintroducing the next one.

“The reintro­duction piece shines a light on the one food that doesn’t agree with you, and it’s much simpler to just avoid that one going forward.”

Take note of how your body reacts. “The reintro­duction piece shines a light on the one food that doesn’t agree with you, and it’s much simpler to just avoid that one going forward.”

When it comes to allergies — and the conditions that can masquerade as allergies, such as lactose intolerance or chemical sensitivities — it’s important to get a clear diagnosis and understand what you’re dealing with. “You can develop a new allergy, and you can grow out of one,” Gupta says. Immunotherapy can be an option for food allergies, and medications can be helpful for conditions such as IBD.

She also suggests looking for connection and support. Advocacy organizations and support groups for people with food allergies or GI disorders share resources and strategies for navigating schools or the workplace. (It’s possible to connect in person and virtually.)

One silver lining to the increase in these conditions is the growth in understanding and accommodation. Gupta notes that 85 million people in the United States now avoid buying some type of food because either they or someone in their household is reactive to it. “You’re not alone,” she says. “Even if it feels that way.”

This article originally appeared as “Making Sense of Food Allergies” in the May 2022 issue of Experience Life.

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