If you’re among the 15 to 20 percent of people who suffer from food intolerance, you know how frustrating it can be to try to pinpoint the problem—and find lasting relief. (1) In fact, you might not even be sure if you’re having food intolerance symptoms, or if what you’re experiencing is due to something else.

Before you can tackle the problems you’re experiencing, it’s important to understand the difference between food allergies, sensitivities, and intolerances.

Food allergy vs food intolerance vs food sensitivity

A food allergy is different than a food intolerance, which, according to some sources, is different than a food sensitivity. (5) Here’s a quick primer on the difference between the three.

Food allergies

Only 2 to 5 percent of people have true food allergies. (1) When you’re allergic to a food, your immune system reacts to it as it would to a harmful invader. Your immune system kicks in, causing your cells to release a substance called immunoglobulin E (IgE) to counteract the allergen.

From that point on, whenever you’re exposed to that same food, your body releases histamine, which can lead to telltale allergic reactions—hives, trouble breathing, digestive problems, etc. (2)

close up of child's hand holding peanuts

Food allergy reactions come on quickly and have the potential to be life-threatening.

The most common food allergies in the United States are eggs, milk, peanuts, tree nuts, wheat, shellfish, and soy. (3) If you have a food allergy, there’s no safe amount of the offending food that you can eat. Even the tiniest bit can trigger the immune system to respond.

Food intolerances

A food intolerance, on the other hand, does not involve the immune system. It’s usually an inability to digest certain foods. (9)

Food intolerances can have a number of causes, which can be either functional issues or structural issues. (1) Lactose intolerance is an example of a functional intolerance—the small intestine lacks the enzyme (lactase) needed to digest lactose.

The diverticular disease would be an example of a cause of structural intolerance. People with diverticular disease might not be able to tolerate nuts, seeds, or popcorn because those small, hard foods can get trapped in the diverticula and trigger an infection.

Common food intolerances include lactose, gluten, fermentable carbohydrates (FODMAPs), and caffeine.

Symptoms of food intolerance are usually digestive disruptions—bloating, gas, and diarrhea are typical reactions. But sometimes it can also cause headaches, fatigue, or brain fog. (4)

Unlike with food allergies, people with food intolerances can sometimes still have small amounts of the offending food without a reaction. For instance, someone who’s lactose intolerant may be able to have small amounts of dairy without getting sick.

Food sensitivity vs food intolerance

The terms food sensitivity and food intolerance are often used interchangeably. However, some sources make a distinction between the two.

The website Healthline, for instance, explains that food sensitivities do involve the immune system, whereas food intolerances do not. Unlike with food allergies, though, which trigger IgG antibodies, food sensitivities are described as involving immunoglobulin G (IgG) antibodies. (5) Food sensitivities can also cause reactions hours or days later, according to the same article.

How to tell if you have a food allergy, intolerance, or sensitivity

If you suspect you may have a food allergy, intolerance, or sensitivity, you should talk to your healthcare provider. Food allergy reactions can require immediate attention and medication. Allergists can run tests to determine what foods or ingredients you’re allergic to so you can be sure to avoid them. (6)

health practitioner talking to patient about a diet plan

A healthcare practitioner can help identify food sensitivities and intolerances and help with building a diet plan!

For food intolerances and sensitivities, it can be harder to identify the culprit. Sometimes the taboo food is obvious—like with lactose intolerance, for example. But in other instances, the food (or foods) can be harder to peg. For instance, if you’re sensitive to yeast, you may think you have a gluten intolerance since you feel lousy whenever you eat bread.

Do IgG food sensitivity tests work?

In addition, while tests do exist for food sensitivities and intolerances, there’s a lot of controversy about their reliability. To understand why let’s first take a look at how some of the more popular tests—the IgG food sensitivity tests—work.

When you have an IgG test done, your healthcare provider will draw blood from you and send it to the lab for testing. There, the blood will be exposed to a number of different foods and food components—sometimes around 100. The lab will be looking to see how much IgG antibody binds to each food. (7)

When you get your results, you’ll see pages of specific foods and food components. Your sensitivity to each food will be noted based on the IgG antibody levels produced when your blood was exposed to the food.

IgG tests are very popular, especially among integrative or holistic practitioners. But some more mainstream medical organizations argue that they’re not reliable. One of the reasons is that some research has shown that higher IgG antibody levels can sometimes indicate higher tolerance to a food item, not lower. (8)

If you’re considering a food sensitivity blood test, it’s worth having a frank discussion about it with your healthcare provider to find out if it’s right for you.

The elimination diet for food intolerance

One tried-and-true—though decidedly less convenient—way to figure out what foods are triggering you is the elimination diet.

With the elimination diet, as the name suggests, you’ll eliminate all potentially problematic foods from your diet. Then very slowly, over the course of weeks or months, you’ll add each food back one at a time and watch for a reaction.

woman making a smoothie with vegetables

To benefit from the elimination diet, you’ll want to write down every single food you eat while also monitoring symptoms that trigger you.

An essential component of the elimination diet is a detailed food diary. You’ll want to write down every single food you eat while also monitoring your symptoms. The key is to be hyper-specific so you can figure out whether it’s a specific ingredient, rather than a complete food group, that’s causing your troubles.

An elimination diet can be very challenging to adhere to, and it can also be confusing to interpret results. So make sure you do it with the help of a knowledgeable healthcare provider.

The bottom line

Food intolerances can be frustrating, and they can make you feel like you’re living on a very limited diet. But for many people, once they really pinpoint their intolerances, they find that possibilities open for them.

In some cases, as with lactose intolerance, you may still be able to consume dairy. You’ll just need to take lactase (the enzyme that digests lactose).

In other cases, you’ll simply need to avoid the foods you’ve identified as triggers. That can take some adjustment, but once you learn to work around your food intolerances, you’ll find that you have control over them—instead of the other way around.

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