Food Intolerance Is Real—but It’s Not the Same as an Allergy, Expert Interview

The differences between food intolerances and allergies come down to severity, reaction time, and curability, Dr. Hart explains.

breads, toast coffee on a wood table. food intolerances are important to pay attention to.
Credit: Food allergy vs intolerance: What's the big difference? Learn what a doctor says.

In a world where we’re more and more in tune with our bodies and our reactions to different foods, a slew of words surrounding the things we choose not to eat have emerged. But what should make things clearer often makes the universe of food aversion more oblique. Your cousin says she’s “allergic to wheat,” but cheats on Saturdays while your niece has to carry an EpiPen because of her anaphylactic reactions to peanuts. You know you feel better when you avoid dairy, but when you make exceptions at the holidays, nothing terrible happens except a bit of acne. (The same can’t be said for your best friend with Celiac, who stopped speaking to her roommate when she “snuck” some non-GF-flour into her birthday cake.)

These differences aren’t just dividing friendship groups; they’re real issues. Dr. Gill Hart, a biochemist and food intolerance expert from YorkTest, pioneers in food intolerance testing, is the perfect person to make this world a little bit easier to understand.

Because of this confusion around allergies and intolerances, it could be that people think they have an allergy when actually they have an intolerance or sensitivity. Do you have experience with allergies or intolerances? What sets off your symptoms, and how did you find out? Leave a comment below to let us know.

Dr. Hart sat down with Organic Authority to set the record straight once and for all. Here’s our interview, condensed and edited for clarity. 

a bowl of nuts, common food allergy but not intolerance

OA: What’s a food allergy?

Dr. Hart: Food allergies stand out from food intolerances, first and foremost, due to the timing and severity of the reaction. Allergies cause an immediate reaction that could be life-threatening, in the case of anaphylaxis.

The sort of symptoms you might get are things like tingling in the lips, swelling in the mouth and throat, nausea, vomiting, diarrhea, but within a few minutes, usually, of eating the food. Common food allergens include milk, eggs, tree nuts, peanuts, and shellfish.

We’re becoming much more aware of things like sesame and soy as well. The top food allergens for American adults are shellfish, peanuts, and tree nuts; American children, meanwhile, are most commonly allergic to milk, eggs, and peanuts.

Allergies tend to stick around—at least if you develop them as an adult. While children can occasionally grow out of them, allergies, once into adulthood, tend to be for life. 

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soy, a common food allergy, growing on a vine. Learn food intolerance vs food allergy on OA

OA: What causes allergies?

Dr. Hart: When you have an immune reaction, you have a reaction to the protein in the food. A lot of allergies can become worse with time, because people aren’t aware of the links between some of the proteins.

This is the case, for example, with allergies to latex, pineapple, avocados, and bananas, all of which have quite similar proteins. There’s a sort of cross-reactivity that happens.

From a medical perspective, allergies can be identified via skin prick and antibody testing.

Allergies always involve the antibody type IgE. This antibody is produced very, very quickly for the person who’s allergic. And then it goes on to cause symptoms of an allergy.

About 32 million people have allergies in the U.S.—about 10 percent of the total population, which is higher than in other countries such as the UK.

sipping coffee in the sun with trees behind her. Does she know the difference between a food intolerance vs food allergy?

OA: Why do so many people have allergies?

Dr. Hart: It’s difficult to tell, actually, and there’s a lot of different theories around allergies, as to why they’re on the increase. Some people believe it’s because children are not always exposed to things when they’re young, and we live in a much more clean environment now than we used to.

Other reasons could be down to when kids are exposed to different foods, or simply how data is collected.

Perhaps most importantly, I would stress that with an allergy, medical attention is required. Whatever age you are, this isn’t something you can manage yourself.

OA: What’s a food intolerance?

Dr. Hart: Food intolerances and sensitivities are a whole other ballgame, albeit one that encompasses both terms, which can be used interchangeably, though the term “intolerance” is preferred in the UK. They are markedly different from allergies, both in terms of the timing of the reaction and its severity.

Food intolerances are not life-threatening, but can still be very impactful.

Typically, intolerances and sensitivities are delayed reactions that can take up to three days to actually manifest themselves.

feeling tired from food intolerance, or a food allergy

OA: What are food intolerance symptoms?

Dr. Hart: Symptoms may include migraines, digestive problems, IBS, constipation, diarrhea, bloating, low energy, low mood, skin rashes, acne, psoriasis, joint pain, rhinitis, and respiratory issues.

Given their delayed, less acute symptoms, many people aren’t even aware they have a food intolerance at all.

A lot of people feel tired, and they think that feeling tired or low in mood or tummy problems are normal for them. They don’t really associate them with a food intolerance.

bags of legumes. anything with a protein in it can cause food allergy, unlike food intolerance

OA: How is a food intolerance diagnosed?

Dr. Hart: IgG antibodies—the kind YorkTest tests for—indicate an immune response linked to a food intolerance or sensitivity.

We find that people that go on to do an elimination diet based on that IgG reaction actually report back to us that they feel better.

Intolerances affect a larger proportion of the population than allergies—I estimate 45 percent—and can be a reaction to a wider range of food.

Any food that has a protein in it or a large molecule has the ability to form an IgG response. Possible culprits include wheat, gluten, milk, yeast, and even vegetables, fruits, lentils, and more.

Luckily, unlike with allergies formed in adulthood, sometimes eliminating a food one is intolerant to is simply a temporary solution.

The interesting thing with intolerances is that they aren’t necessarily for life. Once you’ve actually given your gut a rest from that food for around three months, you can start to reintroduce the food gently back into your diet. And some people can tolerate the food again, after giving the body a rest.

And this goes doubly true if you’re taking good care of your gut in the meantime with probiotics and digestive enzymes.

pouring milk into a glass jar with coffee. dairy intolerance is real, but it's important to know the difference between allergy vs. intolerance.

OA: Are lactose intolerance and celiac disease considered allergies?

Dr. Hart: Long before we started talking about food intolerances in the mainstream, one of the only commonly documented intolerances was one to lactose – which, it turns out, is totally different from either an allergy or an IgG reaction.

This is because lactose is a milk sugar rather than a protein. You cannot have an IgG or an IgE reaction—an allergy or a traditional food sensitivity or food intolerance—to milk sugar. It’s too small a molecule.

Lactose intolerance is actually an enzyme deficiency—specifically lactase. It can be genetic, and keeps people from being able to break down lactose, which contributes to unpleasant digestive symptoms. While you cannot do a blood test for lactose intolerance, you can do a breath test for it, which involves measuring hydrogen in the breath.

In addition to this form of lactose intolerance, milk allergies and sensitivities are also possible. These reactions are linked to the milk protein rather than the milk sugar, and they can even coexist with lactose intolerance. While one can sometimes cure a milk intolerance, milk allergies and lactose intolerance are both usually lifelong ailments.

There’s perhaps no food more closely entwined in this issue than wheat, and specifically gluten. You can have an allergy to wheat, although it’s not actually very common.

More common are gluten intolerances, which come in several forms. Celiac disease is a serious auto-immune condition whereby the consumption of gluten causes irreparable damage to the gut and may later cause nutrient deficiencies; it affects around two percent of the population, and is not an intolerance of the kind YorkTest tests for. 

Celiac aside, non-Celiac gluten sensitivity is quite common—more common than a wheat allergy—and can indeed be overcome with time and work repairing the gut.

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breads, toast coffee on a wood table. food intolerances are important to pay attention to.
Credit: Food allergy vs intolerance: What’s the big difference? Learn what a doctor says.

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Emily Monaco is a food and culture writer based in Paris. Her work has been featured in the Wall... More about Emily Monaco