Food Allergy 101

Food Allergy 101: Understanding Food Reactions

Constant fatigue. Waking up exhausted even after a full night's sleep. Brain fog that won't lift. Digestive issues that come and go without any obvious pattern. Skin problems that don't respond to treatment. Anxiety or depression that seems to appear from nowhere.

These symptoms don't seem related to food. But they often are.

Food allergies and sensitivities are one of the most underdiagnosed contributors to chronic health problems. Not because they're rare. Quite the opposite. Because they're so common and so varied in their symptoms that most people and most doctors miss them entirely.

Understanding how food reactions work is essential for understanding why you feel the way you do and what you can do about it.

Two Types of Food Reactions

Food reactions fall into two fundamentally different categories, and understanding this distinction is critical.

Type 1: Immediate Reactions (True Allergies)

These are what most people think of when they hear "food allergy." Peanut allergies. Shellfish allergies. The reactions that can send someone to the emergency room.

Immediate reactions are IgE-mediated. Your immune system produces Immunoglobulin E (IgE) antibodies against specific food proteins. When you eat that food, the IgE antibodies trigger mast cells to release histamine and other inflammatory compounds within minutes to hours.

Symptoms appear fast: hives, swelling, difficulty breathing, anaphylaxis in severe cases. These reactions are consistent, immediate, and obvious. You eat the food, you react, every time.

This is a fixed immune response. Your body has permanently marked that food as dangerous. The allergy doesn't fluctuate based on how much you eat or how often. A tiny amount can trigger a reaction.

True IgE allergies affect about 4-6% of children and 3-4% of adults. They're serious, they're well-recognized by conventional medicine, and they require strict avoidance.

Type 2: Delayed Reactions (Sensitivities)

These are the reactions that conventional medicine often misses entirely. They're IgG or IgA-mediated, not IgE.

Delayed reactions can take anywhere from several hours to three days to appear. This delayed timeline makes them nearly impossible to identify without proper testing, because you don't connect the food you ate on Monday with the headache or bloating you experience on Wednesday.

Unlike fixed IgE allergies, delayed sensitivities are often dose-dependent and cyclical. You might tolerate small amounts occasionally but react when you eat larger quantities or eat the food frequently.

The reaction severity can fluctuate based on your overall gut health, stress levels, and how much inflammation you're already dealing with. Some days you might tolerate a food that wrecks you other days.

This variability makes delayed reactions confusing and frustrating. You think "I ate eggs last week and was fine, so eggs can't be the problem." But that's not how IgG/IgA reactions work.

Why Delayed Reactions Develop

True IgE allergies are relatively straightforward. You're born with a genetic predisposition, you get exposed to the food, your immune system overreacts, and you develop a lifelong allergy.

Delayed food sensitivities are different. They develop because something went wrong with your gut.

When your intestinal barrier becomes permeable (leaky gut), large protein molecules that should stay in your digestive tract slip through into your bloodstream. The mechanism involves zonulin, tight junctions, and multiple causes including stress, inflammation, SIBO, and certain medications.

Your immune system sees these large food proteins in your bloodstream and identifies them as foreign invaders. It mounts an attack by producing IgG or IgA antibodies against them.

The more frequently you eat that food while your gut is leaky, the stronger the antibody response becomes. This is why food sensitivities tend to get worse over time if the underlying gut dysfunction isn't addressed.

Common Symptoms of Food Sensitivities

This is where food sensitivities get tricky. The symptoms extend far beyond digestive issues.

Digestive: Gas, bloating, diarrhea, constipation, stomach pain, nausea, acid reflux. These are the obvious ones. If you have IBS, food sensitivities are almost certainly involved.

Neurological: Brain fog, difficulty concentrating, memory problems, headaches, migraines, mood swings, anxiety, depression. Many people don't realize that food reactions can affect brain function, but they absolutely can. Inflammatory cytokines cross the blood-brain barrier.

Energy: Chronic fatigue, post-meal crashes, feeling exhausted after eating, difficulty getting out of bed despite adequate sleep. Food should give you energy. If it's making you tired, you're reacting to something.

Skin: Acne, eczema, rosacea, psoriasis, unexplained rashes, dry skin, hives. Skin is often the first place inflammation shows up.

Immune: Frequent colds and infections, seasonal allergies getting worse, autoimmune flares, chronic inflammation. About 80% of your immune system lives in your gut. When your gut is inflamed from food reactions, your entire immune system becomes hypervigilant.

Joint and Muscle: Joint pain, muscle aches, stiffness, inflammatory arthritis symptoms. Many people with joint pain improve dramatically when food sensitivities are addressed.

Respiratory: Chronic congestion, post-nasal drip, asthma exacerbation, frequent sinus infections. Airborne allergies often improve when food sensitivities are eliminated.

The diversity of symptoms happens because immune responses create systemic inflammation. Those inflammatory signals can affect any tissue in your body.

The Big Five Food Sensitivities

While people can develop sensitivities to almost any food, five categories show up most frequently in testing:

1. Gluten and Grains

This is the most prevalent category and, in my clinical experience, places the biggest strain on the immune system.

Gluten (specifically gliadin) triggers zonulin release, which opens tight junctions in your gut lining. This increases intestinal permeability in everyone who eats it, not just people with celiac disease.

Beyond gluten, all grains contain lectins, phytates, and other compounds that can irritate the gut lining. Many people who go "gluten-free" but continue eating corn, rice, and oats don't see improvement because they're still eating inflammatory grain proteins.

2. Corn

Corn is technically a grain, but it deserves special mention. It's highly genetically modified, heavily sprayed with glyphosate, often contaminated with mycotoxins, and extremely inflammatory for most people.

Corn wreaks havoc on gut bacteria, creating dysbiosis that further damages the intestinal barrier. Don't forget about high-fructose corn syrup, which appears in thousands of processed foods and drives both inflammation and metabolic dysfunction.

3. Dairy

Dairy causes problems through two mechanisms: lactose intolerance (inability to digest milk sugar) and casein sensitivity (immune reaction to milk protein).

About 65% of the global population loses lactase enzyme production after weaning. Undigested lactose gets fermented by gut bacteria, creating gas, bloating, and diarrhea.

Casein is a large protein that easily crosses a leaky gut barrier and triggers immune responses. Dairy also increases mucus production in many people, which can worsen respiratory and sinus issues.

4. Soy

Soy has strong estrogenic activity that can severely disrupt hormonal balance. It affects ovaries, testicles, uterus, breast tissue, and prostate.

Like corn, soy is heavily genetically modified and sprayed with glyphosate. It's also high in phytoestrogens that bind to estrogen receptors and can create hormonal chaos.

5. Sugar (and High-Glycemic Carbohydrates)

Sugar isn't technically an allergy or sensitivity, but overconsumption severely imbalances your immune system and feeds pathogenic bacteria in your gut.

High sugar intake creates inflammation, promotes SIBO (bacterial overgrowth), damages the gut lining, and suppresses immune function. It also drives insulin resistance, which creates its own cascade of problems.

Testing for Food Sensitivities

You can't reliably identify delayed food sensitivities based on symptoms alone. The delayed timeline makes it nearly impossible to connect cause and effect without testing.

IgG/IgA Blood Testing: Lab panels measure antibody levels to 90-200+ foods. These tests show what your immune system has been producing antibodies against, which indicates foods you've been reacting to.

Standard allergy testing (skin prick tests or IgE blood tests) only identifies immediate allergies. They completely miss delayed sensitivities, which are far more common.

Applied Kinesiology Testing: Muscle testing can identify foods your body is reacting to in real-time by assessing how your nervous system responds when exposed to specific food antigens. This is particularly useful for identifying hidden sensitivities and assessing digestive enzyme function.

Elimination Diet: The gold standard is systematic elimination followed by reintroduction. Remove suspect foods for 3-4 weeks (long enough for antibody levels to drop and inflammation to settle), then reintroduce one food at a time while monitoring symptoms.

A comprehensive elimination protocol removes all common trigger foods, then systematically tests them to identify your personal triggers.

The Gut-Immunity Connection

Here's the key insight that conventional medicine misses: food sensitivities are a symptom of gut dysfunction, not a standalone problem.

About 80% of your immune system lives in your gut. When your gut lining is damaged, your bacterial balance is disrupted, or your digestive function is impaired, your immune system becomes hypervigilant.

This is why many people with food sensitivities also struggle with seasonal allergies. The root problem is immune hypervigilance driven by gut dysfunction. Fix the gut, and both food sensitivities and environmental allergies often improve.

The Stress Connection

Stress doesn't just make food sensitivities worse. It can cause them.

When you're under chronic stress, cortisol production becomes dysregulated. Cortisol normally helps control inflammation throughout your body, including in your gut.

When cortisol is depleted, you lose that inflammatory control. Your gut lining becomes inflamed, tight junctions loosen, permeability increases, and food proteins slip through that shouldn't.

You might be more stressed than you realize, and that stress is directly contributing to your food reactions.

Managing stress isn't optional for healing food sensitivities. It's foundational.

Can Food Sensitivities Be Reversed?

Unlike true IgE allergies, delayed food sensitivities can often be reversed.

The key is addressing the underlying gut dysfunction: heal the leaky gut by removing inflammatory triggers and supporting tight junction repair, treat SIBO or other bacterial imbalances, restore adequate stomach acid and enzyme production, manage stress and support adrenal function, reduce systemic inflammation.

When the gut barrier is restored and inflammation settles, IgG and IgA antibody levels drop. Foods you were reacting to can often be successfully reintroduced.

I've seen countless patients go from reacting to 15-20 foods down to zero after 6-12 months of gut healing work. But it requires addressing the mechanisms, not just avoiding foods forever.

The Bottom Line

Food allergies and sensitivities are more common than most people realize and more varied in their symptoms than conventional medicine acknowledges.

If you have chronic health issues that haven't responded to standard treatment, food sensitivities are worth investigating. Especially if you have digestive issues, fatigue, brain fog, skin problems, or autoimmune conditions.

Testing identifies the foods you're currently reacting to. Elimination protocols help manage symptoms while healing. But the real work is fixing the gut dysfunction that allowed the sensitivities to develop in the first place.

Your body isn't broken. Food isn't inherently toxic. But when your gut is compromised, normal foods can trigger abnormal reactions.

Fix the gut, and the food reactions often resolve themselves.

For comprehensive nutrition strategies that support gut healing and reduce food sensitivities, visit the Fuel Your Body pillar page.

For stress management and adrenal support protocols that reduce gut inflammation, visit the Regulate Your System pillar page.

Ready to optimize your health and performance? Dr. JJ Gregor uses Applied Kinesiology and functional health approaches to identify food sensitivities and heal the gut dysfunction causing them at his Frisco, Texas practice. Schedule a consultation to discover how comprehensive food sensitivity testing, elimination protocols, and gut healing strategies can restore your health.