How to Tell the Difference Between a Food Allergy, Sensitivity, and Intolerance
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Understanding food allergies, sensitivities, and intolerances can help you reduce inflammation and feel clearer, calmer, and more comfortable in your body.
Start tracking your symptoms and meals to uncover hidden food triggers with simple, focused journaling.
Ready to dig deeper? Take the free FODMAP Quiz to discover if FODMAPs might be part of your digestive story.
This is for you if you’ve made healthy changes but still struggle with bloating, brain fog, joint pain, or unpredictable symptoms.
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You’ve probably heard of food allergies, sensitivities, and intolerances before, but no one’s ever really explained how they could be part of your story.
Maybe you’ve been making positive changes: eating more whole foods, cutting back on sugar, moving your body more. But still, your symptoms linger, including bloating, headaches, fatigue, skin flare-ups, and mood swings.
It can be confusing, especially when these reactions feel random or delayed.
I see this all the time in my work as a holistic nutritionist and gut health expert. Many of my clients start their journey with me doing all the “right” things, but still feel off. One of the most overlooked reasons is how their body is reacting to certain foods.
What makes this tricky is that food reactions don’t always show up immediately, and they don’t always look the same. That’s why understanding the difference between an allergy, a sensitivity, and an intolerance can be a game-changer.
Let’s break down what each one means and explore whether your patterns point to a possible food reaction.
Understanding Food Allergy, Sensitivity, and Intolerance
Let’s break down the three major types of food reactions so you can start figuring out which one might be part of your story.
Food Allergy (IgE-Mediated Reaction)
This is a fast and dramatic immune response. Your body produces IgE antibodies to fight off a food it sees as dangerous. Symptoms usually show up within minutes (or up to two hours) and can include things like hives, swelling, and even difficulty breathing or anaphylaxis. These reactions are hard to miss, often serious, and usually easy to trace back to a specific food.
Food Sensitivity (IgG-Mediated Reaction)
This is the slow-burn immune response. Your body produces IgG antibodies that latch onto the offending food and form immune complexes, which gradually trigger inflammation. Symptoms can take hours (or even days) to appear, and they can show up just about anywhere: brain fog, fatigue, migraines, joint pain, skin issues, digestive symptoms, and more. Because of the delay, it’s much harder to connect the dots.
Food Intolerance (Non-Immune Reaction)
This one isn’t about your immune system, it’s about digestion. Your body simply has trouble breaking down a specific component in a food (like lactose in dairy or fructose in fruit). The result? Gas, bloating, cramping, and irregularity. These symptoms can show up much later, which also makes it hard to pinpoint the source.
Vegetables and legumes like cauliflower, beans, kale, radishes, and chickpeas can be difficult to digest for some people, especially in larger amounts. These higher FODMAP foods are common culprits behind food intolerances that lead to bloating, gas, or cramping.
With food allergies, if you accidentally eat the trigger food, your body lets you know, fast and loud. And because the reaction is so intense, it’s usually easy to avoid that food in the future.
But sensitivities and intolerances? They’re subtle. Easy to miss. Easy to dismiss.
You know… if that nightly bowl of ice cream leaves you bloated and uncomfortable, but you’re already in your jammies and on the couch, what’s the harm really?
Well, we’re all adults here, but the harm is that you never feel amazing.
And over time, those small, repeated reactions can drive up inflammation and lead to bigger problems.
Why Knowing the Difference Changes Everything
Understanding whether you’re dealing with a food allergy, sensitivity, or intolerance can be a total game-changer, especially if you’ve been chasing answers but still feel stuck in a cycle of “maybe this will help?”
Here’s why it’s worth paying attention:
Food sensitivities are underdiagnosed. While true food allergies are estimated to affect 5-20% of the population, delayed-onset food sensitivities are harder to quantify. Many people experience symptoms without ever realizing food is the trigger because the reaction doesn’t always happen right away. That disconnect makes it easy to miss… and even easier to live with symptoms you don’t have to.
The symptoms aren’t always in your gut. These reactions can affect your joints, skin, sinuses, mood, and energy levels, depending on where inflammation settles in your body. One person gets migraines, another has eczema, and someone else just feels tired all the time. That’s why it can feel so confusing.
Cravings can cloud the picture. Foods like gluten and dairy can create an opioid-like “feel-good” response in your brain. So you eat them, feel better temporarily, and reach for them again without realizing they’re feeding inflammation and your immune response. Then, when you try cutting them out, you feel worse at first. That withdrawal effect can really muddy the waters.
Symptoms are easy to dismiss. Low-grade, lingering symptoms like brain fog, bloating, joint aches, or anxiety are often chalked up to stress, hormones, or just getting older. And because they’re not dramatic, it’s easy to push them aside… until they add up.
You don’t have to guess. You can uncover the hidden patterns. Maybe you discover that high FODMAP food intolerances are the key driver behind your symptoms, or that almonds are triggering a sensitivity. The key is slowing down and staying curious, because your body is communicating. You just need time to understand the language.
Curious if FODMAPs might be part of your story? Take the FODMAP Quiz to find out and discover whether this could be the right path for you, or if another approach might serve you better.
If you're still wondering what’s really behind your symptoms, you’re not alone. The FODMAP Quiz helps you uncover whether high-FODMAP foods could be playing a role, or if another path might be the next step.
How to Identify and Address Food Reactions
You don’t have to memorize every reaction type, but a basic understanding of how each one works can help you start connecting the dots in your own experience.
Here are the two most important steps you can take to start improving your symptoms:
Step 1: Understand the Three Types of Food Reactions
Food Allergy (IgE-Mediated Reaction)
This is your immune system’s fast-track alarm system. After eating a food your body sees as a threat, symptoms usually show up quickly (within minutes to two hours) and may include:
Hives
Swelling
Itching
Trouble breathing
In severe cases, anaphylaxis
These reactions are intense and hard to miss. And once you know your trigger, it’s usually easy to avoid it moving forward.
Common culprits include:
Shellfish
Peanuts
Tree nuts (like walnuts)
Milk
Eggs
Soy
Wheat
Fin fish
In fact, these eight foods account for about 90% of all food allergies.
Gluten and wheat are among the most common food triggers, and they can show up in all three types of reactions. Whether it’s a fast-acting allergy, a delayed sensitivity, or a high FODMAP intolerance, bread is a food worth paying attention to as you connect the dots.
Food Sensitivity (IgG-Mediated Reaction)
This is your immune system’s slower, sneakier response. After eating one of these reactive foods, your body starts forming “immune complexes” that build up over time and quietly trigger inflammation, sometimes hours or even days later.
Remember, symptoms can show up almost anywhere: your gut, joints, brain, skin, sinuses, and even your mood.
Because the reaction is delayed and the symptoms are so varied, food sensitivities are often missed or mistaken for something else entirely.
Common symptoms may include:
Bloating, gas, constipation, or diarrhea
Headaches or migraines
Brain fog, fatigue, or mood swings
Skin rashes or itching
Joint or muscle pain
Chronic sinus issues
Insomnia or disrupted sleep
Common culprits include:
Wheat
Cow dairy
Corn
Eggs
Brewer’s yeast
Chocolate
Red kidney beans
Garlic
Food Intolerance (Non-Immune Reaction)
Unlike allergies or sensitivities, this type of reaction has nothing to do with your immune system. Instead, it’s a digestion issue. Your body simply doesn’t have the right tools (like specific enzymes) to properly break down certain food components.
You’ve probably heard of lactose intolerance, but other high FODMAP foods are also common offenders. Because symptoms can show up hours later, and vary in intensity, it’s easy to overlook the connection.
Common signs include:
Gas and bloating
Cramping
Diarrhea or constipation
Abdominal pain and discomfort
Common culprits include:
Lactose (milk sugar found in dairy)
Fructose (fruit sugar found in fruit, honey, and high-fructose corn syrup)
Other FODMAP-rich foods (both lactose and fructose are types of FODMAPs. )
Now that you know how to spot the different types of food reactions, let’s talk about how to actually uncover which ones might be affecting you.
Not sure what FODMAPs are? Check out my FODMAPs 101 blog to learn more.
Not sure where to start with FODMAPs? Check out my FODMAP 101 blog: a quick guide to help you understand what they are, why they matter, and how they might be contributing to your symptoms.
Step 2: Use a Journal to Connect the Dots
Food sensitivities can be tricky to spot because symptoms don’t always show up right away. That’s exactly why a Food and Observation Journal is such a powerful tool; it helps you uncover those hidden patterns.
Here’s how to make the most of it:
Track the Time:
When do your symptoms appear?
Is it hours later… or maybe even days after eating?
Do symptoms come and go, leaving you feeling “off” but unsure why?
Look for Symptom Patterns:
Bloating two days after dairy?
Joint pain the day after corn?
Fatigue creeping in after your weekly pizza night?
Investigate Common Offenders:
Start with investigating one or more of these: wheat, cow dairy, corn, eggs, chocolate, and garlic.
Choose Your Next Step:
Keep observing for 1-2 weeks to see if any clear patterns emerge.
Try a 3-week elimination of a suspected food to notice how you feel without it.
If needed, and with the right guidance and support, consider a short-term elimination of several common offenders to zero in on triggers.
Remember: this is your journey, and every little insight brings you closer to feeling your best.
Ready to get started? Download your free 7-Day Food & Observation Journal to help you track symptoms, spot patterns, and take control of your digestive health.
Once you start noticing which foods tend to trigger your symptoms, tools like your 7-Day Food & Observation Journal can help you connect the dots without the overwhelm of eliminating everything at once.
Frequently Asked Questions
Q: Are food sensitivity tests helpful?
A: They can offer some insight, but they’re not always reliable. If you choose to do an IgG food sensitivity test, think of it as a snapshot of how your body is reacting right now. Often, your food and symptom journal, along with ongoing awareness of how you feel after eating, can be the most accurate and cost-effective tool you have.
Q: Do I have to eliminate every food I react to?
A: Not necessarily. I usually recommend starting by eliminating the most obvious culprits for 3-6 weeks, then reintroducing it to see how your body responds. Sometimes, a little healing makes a big difference in what you can tolerate. You might find you can tolerate a food sensitivity 1-2 times per week, or handle smaller portions if it’s a food intolerance. The key is to focus on empowered awareness, not restriction, and give your body time to heal before testing your limits.
Final Thoughts: Heal on Your Terms
You’ve spent time navigating confusing symptoms, wondering if it’s something you ate, or assuming “this is just how things are now.” But now that you understand the difference between food allergies, sensitivities, and intolerances you can move from guessing to knowing.
You’re no longer sidelined by symptoms without insight.
You can build a solid foundation of change using the tools and knowledge to spot the patterns that once felt invisible.
Here’s the truth: while many people believe food allergies are rare, immune and non-immune reactions to foods are actually far more common than most realize.
That’s why having a clear understanding of what’s happening in your body matters. It helps you make choices that support your health without unnecessary restrictions.
Keep exploring, stay curious, and remember: you have the power to listen to your body and heal on your terms.
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RESOURCES
Shaw W. Clinical usefulness of IgG food allergy testing. Mosaic Diagnostics. Published September 26, 2017. Accessed December 23, 2024. Available from: https://mosaicdx.com/resource/clinical-usefulness-of-igg-food-allergy-testing/