Food Allergy vs Intolerance vs Sensitivity

Food Allergy vs Intolerance vs Sensitivity

Food allergies, intolerances, and sensitivities – oh my!  Adverse food reactions are a topic near and dear to my heart, especially now that I’m trained and certified as a Lifestyle Eating & Performance (LEAP) therapist (“CLT”), and after going through my own holistic gut-healing journey.

Allergies, intolerances, and food sensitivities are actually three totally different beasts… and yes, it’s entirely possible to experience all three types of reactions day-to-day.

After reading this article you’ll learn the key similarities and differences between a food allergy vs intolerance vs sensitivity, how they happen, and what you can do about each of them!

Disclaimer:  This article is meant to be educational, informative and inspiring. This is not medical advice!  Make sure to consult a GI doctor, allergist, functional dietitian, a certified LEAP therapist, a gut health nutritionist, and/or other qualified health practitioners to address your health concerns from a medical nutrition standpoint.

Affiliate disclosure:  This article contains several affiliate links*. As an Amazon Associate, I may make a commission on qualifying purchases at no extra cost to you!

(This article was most recently edited and updated on January 13, 2023.)

Adverse food reactions & dietary restrictions: the struggle is real!

There’s nothing worse than walking into a restaurant, looking at a menu and trying to find SOMETHING (anything) you can eat that won’t send you spiraling into some kind of inflammatory reaction.

At the same time, for those dealing with frequent heartburn, spontaneous hives, brain fog, skin eruptions, joint pain, or of course the dreaded irritable bowel syndrome (IBS) / small intestinal bacterial overgrowth (SIBO) inflammatory bowel disease (IBD) symptoms of gas, bloating, stomach pain, diarrhea, nausea, etc.…

I think it’s safe to say it’s better to know exactly what it is that the body is reacting to, than to not know.  In any of those cases, ignorance is definitely NOT bliss!

Food allergy vs intolerance vs sensitivity – key differences

It’s important to know and understand the key differences in these various types of adverse food reactions, because each of them can have a very different kind of impact on health, quality of life, and recommended treatment protocols.  It’s tricky because there can sometimes be a lot of overlap in types of symptoms!

Types of adverse food reactions

A main difference among food allergies, intolerances and sensitivities is that food intolerances are only related to the digestive system, while food allergies and sensitivities both involve the immune system (in different ways).

Food allergies

Food allergies are a specific type of immune response in which the immune system has flagged something we’ve eaten as a falsely perceived threat to the body.

  • This is more likely to happen in cases of leaky gut, where undigested food particles sneak (or “leak”) into the bloodstream through a damaged gut lining.

In cases of food allergies, our immune system produces a type of antibody called “immunoglobulin E”, or “IgE” for short, in reaction to the first exposure to a specific food. The second time we eat that food, these IgE antibodies circulate the body and attach themselves to mast cells (tissue-specific white blood cells which line the mucous membranes of the body).

An allergic reaction to a food can only take place in the mucous membranes of the body where these mast cells are located.  This includes the gut (for example: sudden onset diarrhea), the throat (swelling/closing up), the skin (acute onset itching and hives), the lungs (trouble breathing) and/or the mouth (itching and tingling).

Allergic reactions can be mild and localized (such as in cases of “oral allergy syndrome”). or life-threatening and systemic (anaphylaxis, which requires an “epi-pen” to prevent the body from going into shock from too-low blood pressure or trouble breathing).

Food intolerances

Food intolerances will show up as digestive symptoms such as gas, abdominal cramping, bloating, and/or diarrhea.  Food intolerances don’t involve the immune system at all; they’re caused by a lack of specific types of digestive enzymes and/or the presence or absence of specific microbes in the gut.

Types of food intolerances

You can become “intolerant” to almost anything, but a few examples of the types of food intolerances I see most often in my functional nutrition clinic include:

  1. Lactose intolerance
  2. Fructose intolerance
  3. Sucrose intolerance
  4. FODMAP intolerance
  5. Fat intolerance
  6. Intolerance to acidic/spicy foods

In cases of lactose intolerance, a person is typically missing or low in the digestive enzyme “lactase” which is responsible for breaking down lactose (natural sugar from milk) in the gut.

  • Based on case study and anecdotal observations, people who are low in certain probiotic gut microbes (such as acidophilus or lactobacillus) can also have trouble breaking down lactose!

If you’re truly lactose intolerant and don’t have a dairy allergy or sensitivity, you should be able to eat “hard cheeses” such as cheddar, Swiss,  Havarti or the likes (they all have zero grams of sugar, therefore are naturally “lactose free”) and yogurt (which has acidophilus or lactobacillus to help break down the lactose). People with lactose intolerance tend to have the most trouble with milk and ice cream but can eat butter, ghee, and many types of cheese (and pizza too!) without any issues.

  • If you find that you can’t eat pizza, butter, ghee, you should consider getting allergy tested and/or food sensitivity tested to rule out a dairy allergy/sensitivity!

Another example of a food intolerance is fructose.

Fructose is most commonly found in fruits, juices, honey, agave nectar, high fructose corn syrup, and certain other foods/sweeteners.

Fructose intolerance is common among people who have a digestive condition called “small intestinal bacterial overgrowth” (SIBO) because it’s in the category of “fermentable oligosaccharides, disaccharides, monosaccharides and polyols” (high FODMAP foods).

5 biggest diet mistakes people make when healing their gut - Jenna Volpe dietitian landing page link

Food sensitivities

Food sensitivities are the most confusing and the most complex for people to understand.  They’re often mistakenly labeled as “allergies” or “intolerances”… but as you now know, that is not the case!

It’s understandable though because diarrhea, a primary symptom of food intolerances, can also be caused by food sensitivities (and sometimes allergies too).

Like food allergies, food sensitivities also involve the immune system; however, the response is not specific to IgE antibodies, and a food sensitivity reaction is not limited to the mast cells located within the mucous membranes of the body.

In a nutshell, food sensitivities are any and all types of immune-mediated reactions that don’t involve IgE.  There are other categories of antibodies that can be involved, and many types of mediators which can be released from various types of white blood cells that make up our immune system.

Symptoms of a food sensitivity can be very delayed (up to 96 hours after eating a food!), and they can also be dose-dependent (so for example we can react after exceeding certain thresholds of foods).  This makes food sensitivities the most difficult to navigate and identify.

Since food sensitivities occur as a result of mediator release, and they involve different types of mediators aside from just histamine, food sensitivity reactions can manifest very differently from person to person depending on where in the body they are taking place.

It’s possible you may have an underlying food sensitivity if you’re experiencing any of the following:

Food sensitivity symptoms

  • Diarrhea-Predominant Irritable Bowel Syndrome
  • Heartburn/GERD
  • Eosinophilic Esophagitis
  • Crohn’s Disease
  • Colitis
  • Cyclic Vomiting Syndrome
  • Interstitial Cystitis
  • Migraines
  • Autism Spectrum Disorders
  • Epilepsy
  • Depression
  • Insomnia
  • Restless Leg Syndrome
  • Fibromyalgia
  • Arthritis
  • Polycystic Ovarian Syndrome (PCOS)
  • Acne
  • Psoriasis
  • Mysterious skin eruptions
  • Unexplainable fluid retention
  • Urticaria (hives)

Although the above conditions are usually linked to other clinical implications, it’s important to rule out and address food sensitivities along the way.  I believe in un-turning as many stones as possible until people are able to get to the underlying root causes of a condition from all angles!  Things always happen for a reason. Whether it’s nutrition-related or energetic, gut-related, genetic, stress-related or something else.

Many health issues can be resolved 90% of the time in my experience if you just keep going. All roads lead to Rome!

Timing of adverse food reactions: key differences

An IgE food allergy is going to occur typically within minutes, or at most within the hour.

Food intolerances are most likely to occur within 30 minutes to a few hours’ time, depending on how quickly the transit time varies from person to person.

Food sensitivities are the most difficult to identify through food-symptom journals alone because we can have a reaction up to 96 hours after consumption of the food.

How to test for a food allergy vs intolerance vs sensitivity

Food allergy 

The best way to rule out food allergies (aside from “oral challenge tests” which can be very scary and traumatizing for people with severe reactions) is to get a skin test and blood test from a doctor at a local allergy clinic.

Gluten allergies can be measured by ruling out celiac disease via a blood test or intestinal biopsy.  A gluten allergy (celiac disease) is different from a gluten intolerance or sensitivity.

  • Cutting out gluten via an elimination diet is not always the best way to rule out a gluten allergy/sensitivity/intolerance – you can learn why here in my free gut health nutrition guide!

Food intolerance

To rule out a lactose intolerance, typically patients at a doctor’s office will be asked to drink an unpleasant amount of milk and they track your symptoms within the next 30 minutes…

Most people opt to go by their clear symptoms caused by drinking milk, and avoid this fun test.

Fructose intolerance and sucrose intolerance can be ruled out via a breath test, but it’s best to consult a GI doctor first because these types of intolerances are usually accompanied by other underlying conditions such as SIBO or dysbiosis.

(The gold standard for sucrose intolerance and even lactose intolernce is to perform a disaccharide biopsy, which can only be done during a colonoscopy or endoscopy… that’s pretty invasive!)

Food-symptom journals, although subjective, can also be helpful in identifying any potential food intolerances (especially when dealing with other types of foods or chemicals in food such as histamine).  It’s possible to react to anything.

(Grab a copy of the IBS Food Diary, designed and published by “yours truly”, if you’d like to take your level of “Symptom Clarity” to the next level!)

  • In my opinion, the process of identifying food intolerances is best done working 1:1 with a registered dietitian who specializes in digestive health, leaky gut and adverse food reactions. (I know, I know… consider the source! But honestly it will save you years of guessing and spare you a whole lot of frustration/confusion/discomfort.)

Food sensitivity 

If you’d like to rule out food sensitivities, first you should make sure you’re a good candidate!

Are you presenting with a bunch of the above symptoms and not responding to conventional medical approaches/cookie cutter diets?

Do you have a healthy relatioship with food and self-care?

Are you someone who is good at implementing and applying what you learn?

(If so, this next step may be very helpful for you!)

The Mediator Release Test (MRT Test)

My preferred method of food sensitivity testing is the Mediator Release Test (MRT), alongside a customized six-part “oligoantigenic” Lifestyle Eating & Performance (LEAP) diet which is co-crafted by you + your LEAP therapist, based on YOUR specific test results.  (Why spend months or years trying to do guess-work when we don’t have to?!)

You must first get screened by a CLT before embarking on that journey, to make sure the MRT test is a good fit for you.

  • MRT is not for everyone, especially for people with eating disorders, since the approach is highly restrictive in the beginning.
    • A healthy relationship with food must precede any and all functional nutrition interventions that involve dietary restriction of any kind.

For those who meet criteria, MRT food sensitivity testing paired with the LEAP eating plan is my preferred method because it’s truly the most holistic and customized approach for addressing food sensitivities!

  • MRT testing measures your body’s reactions from an entire standpoint – it doesn’t just look at certain types of pathways (IgG, IgA, IgE) or certain types of mediators (like histamine); it measures the change in white blood cells’ solid to liquid ratio before and after being exposed to each food and chemical on the panel.
    • This is like walking around and looking at the entire statue as a whole versus just looking at it from the front or the back!

Healing from a food allergy / food intolerance / food sensitivity – how can that happen?

The immune system resides primarily in the gut, so if you can repair gut via the 5R Protocol while supporting your liver, reducing stress and addressing all the other aspects of health impacting your immune system (where allergies reside), you can promote healing and re-balancing of your immune system!

A healthy gut wall & balanced gut microbiome will also allow you to break down foods properly, resulting in less food intolerances over time.

Resolving food sensitivities and other types of adverse food reactions is a slow process and a long game… but it can be done if you’re someone who is highly motivated and who can cultivate a holistic mindset.

More resources

If you’d like to learn more about how food allergies, food sensitivities and food intolerances can impact gut health and how to navigate all of this via a holistic approach, feel free to check out the following articles:


There’s a lot to say about the overlap and the key differences between symptoms and mechanisms of food allergies vs food intolerances vs food sensitivities.

While all 3 types of adverse food reactions can take place in the gut, food allergies and food sensitivity reactions are triggered by imbalances in your immune system, while food intolerances are caused and triggered directly by imbalances in you gut.

The symptoms of food intolerance are ONLY gut-related (i.e. IBS/IBD symptoms), while allergies involve histamine reactions (itching, redness, swelling, hives, etc.).  Food sensivitity reactions can be more broad (IBS-D, IBD, hives, rashes, joint pain, fibromyalgia, migraines, autoimmunity, etc.).

Food allergies and food intolerance reactions are relatively immediate (within an hour or two after eating), while food sensitivity reactions can be delayed and dose-dependent which makes them more difficult to catch.

Keeping a detailed food-symptom journal can be a relatively easy way to look for patterns to identify food allergies and intolerances, but if you’re suspecting you have food sensitivities, you may want to consider working with a functional dietitian and/or certified LEAP therapist to run specialty testing (such as the MRT food sensitivity test if clinically a good fit).

Unfortunately it’s possible to be experiencing all three types of adverse food reactions – I see this a lot in my clinic.

The food & healthcare systems can be confusing and complex, but they don’t have to be, with the right guidance.

If you’d like to learn more about how to dodge some of the most common dietary pitfalls I see people make on their gut-healing journeys, please feel free to download my complimentary gut health nutrition guide: 5 Diet Mistakes to Avoid When Healing Your Gut!

Free Download - 5 Diet Mistakes to Avoid When Healing Your Gut - by Jenna Volpe RDN LD CLT

XO – Jenna

Leave a Comment

Your email address will not be published. Required fields are marked *